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    2023年, 第32卷, 第10期 刊出日期:2023-09-21 上一期    下一期
    Valley polarization in transition metal dichalcogenide layered semiconductors: Generation, relaxation, manipulation and transport
    Hui Ma(马惠), Yaojie Zhu(朱耀杰), Yulun Liu(刘宇伦), Ruixue Bai(白瑞雪), Xilin Zhang(张喜林), Yanbo Ren(任琰博), and Chongyun Jiang(蒋崇云)
    2023 (10):  107201-107201.  doi: 10.1088/1674-1056/ace160
    摘要 ( 245 )   HTML ( 7 )   PDF(7199KB) ( 208 )  
    In recent years, valleytronics researches based on 2D semiconducting transition metal dichalcogenides have attracted considerable attention. On the one hand, strong spin-orbit interaction allows the presence of spin-valley coupling in this system, which provides spin addressable valley degrees of freedom for information storage and processing. On the other hand, large exciton binding energy up to hundreds of meV enables excitons to be stable carriers of valley information. Valley polarization, marked by an imbalanced exciton population in two inequivalent valleys (+$K$ and -$K$), is the core of valleytronics as it can be utilized to store binary information. Motivated by the potential applications, we present a thorough overview of the recent advancements in the generation, relaxation, manipulation, and transport of the valley polarization in nonmagnetic transition metal dichalcogenide layered semiconductors. We also discuss the development of valleytronic devices and future challenges in this field.
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    Perspectives of spin-valley locking devices
    Lingling Tao(陶玲玲)
    2023 (10):  107306-107306.  doi: 10.1088/1674-1056/acc809
    摘要 ( 276 )   HTML ( 7 )   PDF(5558KB) ( 251 )  
    Valleytronics is an emerging field of research which utilizes the valley degree of freedom to encode information. However, it is technically nontrivial to produce a stable valley polarization and to achieve efficient control and manipulation of valleys. Spin-valley locking refers to the coupling between spin and valley degrees of freedom in the materials with large spin-orbit coupling (SOC) and enables the manipulation of valleys indirectly through controlling spins. Here, we review the recent advances in spin-valley locking physics and outline possible device implications. In particular, we focus on the spin-valley locking induced by SOC and external electric field in certain two-dimensional materials with inversion symmetry and demonstrate the intriguing switchable valley-spin polarization, which can be utilized to design the promising electronic devices, namely, valley-spin valves and logic gates.
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    Large valley Nernst effect in twisted multilayer graphene systems
    Guanlin Jian(简冠林), Zhen-Gang Zhu(朱振刚), and Gang Su(苏刚)
    2023 (10):  107202-107202.  doi: 10.1088/1674-1056/acbd2c
    摘要 ( 203 )   HTML ( 4 )   PDF(1851KB) ( 130 )  
    Valley Nernst effect is a newly proposed and experimentally confirmed effect, which could be used to design novel thermoelectric devices. We study the valley Nernst effect in (M+N)-layer twisted multilayer graphene systems by a simple low-energy effective model. It is found that the total valley Nernst coefficient (VNC) is three orders of magnitude larger than that in monolayer group-VI dichalcogenides. The total VNC increases with the increase of layer numbers. It is shown that the total VNC exhibits a structure with three peaks as a function of the Fermi energy. We identify that the central peak is always negative stemming from the flat band. Two shoulder peaks are positively induced by the conduction and valence bands, respectively. These predicted features can be tested experimentally. The present work would shed more light on valley caloritronics.
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    Moiré Dirac fermions in transition metal dichalcogenides heterobilayers
    Chenglong Che(车成龙), Yawei Lv(吕亚威), and Qingjun Tong(童庆军)
    2023 (10):  107307-107307.  doi: 10.1088/1674-1056/aceee5
    摘要 ( 208 )   HTML ( 4 )   PDF(2262KB) ( 107 )  
    Monolayer group-VIB transition metal dichalcogenides (TMDs) feature low-energy massive Dirac fermions, which have valley contrasting Berry curvature. This nontrivial local band topology gives rise to valley Hall transport and optical selection rules for interband transitions that open up new possibilities for valleytronics. However, the large bandgap in TMDs results in relatively small Berry curvature, leading to weak valley contrasting physics in practical experiments. Here, we show that Dirac fermions with tunable large Berry curvature can be engineered in moiré superlattice of TMD heterobilayers. These moiré Dirac fermions are created in a magnified honeycomb lattice with its sublattice degree of freedom formed by two local moiré potential minima. We show that applying an on-site potential can tune the moiré flat bands into helical ones. In short-period moiré superlattice, we find that the two moiré valleys become asymmetric, which results in a net spin Hall current. More interestingly, a circularly polarized light drives these moiré Dirac fermions into quantum anomalous Hall phase with chiral edge states. Our results open a new possibility to design the moiré-scale spin and valley physics using TMD moiré structures.
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    Photoinduced valley-dependent equal-spin Andreev reflection in Ising superconductor junction
    Wei-Tao Lu(卢伟涛), Yue Mao(毛岳), and Qing-Feng Sun(孙庆丰)
    2023 (10):  107403-107403.  doi: 10.1088/1674-1056/aceee6
    摘要 ( 169 )   HTML ( 2 )   PDF(1366KB) ( 134 )  
    The Ising spin-orbit coupling could give rise to the spin-triplet Cooper pairs and equal-spin Andreev reflection (AR) in Ising superconductors. Here we theoretically study the valley-dependent equal-spin AR in a ferromagnet/Ising superconductor junction with a circularly polarized light applied to the ferromagnet. Because of the spin-triplet Cooper pairs and the optical irradiation, eight kinds of AR processes appear in the junction, including equal-spin AR and normal AR, the strengths and properties of which strongly depend on the valley degree of freedom. The AR probabilities for the incident electron from the two valleys exhibit certain symmetry with respect to the magnetization angle and the effective energy of light. The equal-spin AR and normal AR present different features and resonant behaviors near the superconducting gap edges. Due to equal-spin-triplet Cooper pairs, not only charge supercurrent but also spin supercurrent can transport in the Ising superconductors. The differential spin conductance for electron injecting from the two valleys can be controlled by the circularly polarized light.
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    Band engineering of valleytronics WSe2–MoS2 heterostructures via stacking form, magnetic moment and thickness
    Yanwei Wu(吴彦玮), Zongyuan Zhang(张宗源), Liang Ma(马亮), Tao Liu(刘涛), Ning Hao(郝宁), Wengang Lü(吕文刚), Mingsheng Long(龙明生), and Lei Shan(单磊)
    2023 (10):  107506-107506.  doi: 10.1088/1674-1056/acb761
    摘要 ( 170 )   HTML ( 3 )   PDF(1518KB) ( 145 )  
    Spin-valley polarization and bandgap regulation are critical in the developing of quantum devices. Here, by employing the density functional theory, we investigate the effects of stacking form, thickness and magnetic moment in the electronic structures of WSe$_{2}$-MoS$_{2}$ heterostructures. Calculations show that spin-valley polarization maintains in all situations. Increasing thickness of 2H-MoS$_{2}$ not only tunes the bandgap but also changes the degeneracy of the conduction band minimums (CBM) at $K/K_1$ points. Gradual increase of micro magnetic moment tunes the bandgap and raises the valence band maximums (VBM) at $\varGamma$ point. In addition, the regulation of band gap by the thickness of 2H-MoS$_{2}$ and introduced magnetic moment depends on the stacking type. Results suggest that WSe$_{2}$-MoS$_{2}$ heterostructure supports an ideal platform for valleytronics applications. Our methods also give new ways of optical absorption regulation in spin-valley devices.
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    Digital holographic imaging via direct quantum wavefunction reconstruction
    Meng-Jun Hu(胡孟军) and Yong-Sheng Zhang(张永生)
    2023 (10):  100312-100312.  doi: 10.1088/1674-1056/acd8b0
    摘要 ( 176 )   HTML ( 2 )   PDF(1395KB) ( 170 )  
    Wavefunction is a fundamental concept of quantum theory. Recent studies have shown surprisingly that wavefunction can be directly reconstructed via the measurement of weak value. The weak value based direct wavefunction reconstruction not only gives the operational meaning of wavefunction, but also provides the possibility of realizing holographic imaging with a totally new quantum approach. Here, we review the basic background knowledge of weak value based direct wavefunction reconstruction combined with recent experimental demonstrations. The main purpose of this work focuses on the idea of holographic imaging via direct wavefunction reconstruction. Since research on this topic is still in its early stage, we hope that this work can attract interest in the field of traditional holographic imaging. In addition, the wavefunction holographic imaging may find important applications in quantum information science.
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    Long-range interacting Stark many-body probes with super-Heisenberg precision
    Rozhin Yousefjani, Xingjian He(何行健), and Abolfazl Bayat
    2023 (10):  100313-100313.  doi: 10.1088/1674-1056/acf302
    摘要 ( 187 )   HTML ( 2 )   PDF(1092KB) ( 107 )  
    In contrast to interferometry-based quantum sensing, where interparticle interaction is detrimental, quantum many-body probes exploit such interactions to achieve quantum-enhanced sensitivity. In most of the studied quantum many-body probes, the interaction is considered to be short-ranged. Here, we investigate the impact of long-range interaction at various filling factors on the performance of Stark quantum probes for measuring a small gradient field. These probes harness the ground state Stark localization phase transition which happens at an infinitesimal gradient field as the system size increases. Our results show that while super-Heisenberg precision is always achievable in all ranges of interaction, the long-range interacting Stark probe reveals two distinct behaviors. First, by algebraically increasing the range of interaction, the localization power is enhanced and thus the sensitivity of the probe decreases. Second, as the interaction range becomes close to a fully connected graph its effective localization power disappears and thus the sensitivity of the probe starts to enhance again. The super-Heisenberg precision is achievable throughout the extended phase until the transition point and remains valid even when the state preparation time is incorporated in the resource analysis. As the probe enters the localized phase, the sensitivity decreases and its performance becomes size-independent, following a universal behavior. In addition, our analysis shows that lower filling factors lead to better precision for measuring weak gradient fields.
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    Measurement of the relative neutron sensitivity curve of a LaBr3(Ce) scintillator based on the CSNS Back-n white neutron source
    Jian Liu(刘建), Dongming Wang(王东明), Yuecheng Fu(甫跃成), Zhongbao Li(李忠宝), Han Yi(易晗), and Longtao Yi(易龙涛)
    2023 (10):  100703-100703.  doi: 10.1088/1674-1056/acca08
    摘要 ( 145 )   HTML ( 2 )   PDF(2008KB) ( 112 )  
    A scintillator detector consisting of a LaBr3(Ce) (0.5%) scintillator, a photomultiplier tube (PMT), and an oscilloscope were used to study the neutron sensitivities of the LaBr3(Ce) scintillator at the China Spallation Neutron Source (CSNS) Back-n white neutron source in the double-bunch and single-bunch operation modes, respectively. Under the two operational modes, the relative neutron sensitivity curves of the LaBr3(Ce) scintillator in the energy regions of 1-20 MeV and 0.5-20 MeV were obtained for the first time. In the energy range of 1-20 MeV, the two curves were nearly identical. However the relative neutron sensitivity uncertainties of the double-bunch experiment were higher than those of the single-bunch experiment. The above results indicated that the single-bunch experiment's neutron sensitivity curve has a lower minimum measurable energy than the double-bunch experiment. Above the minimum measurable energy of the double-bunch experiment, there is little difference between the measured relative neutron sensitivity curves of the single-bunch and double-bunch experiments of the LaBr3(Ce) scintillator and those of other scintillators with a similar neutron response signal intensity.
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    Multifunctional light-field modulation based on hybrid nonlinear metasurfaces
    Shuhang Qian(钱树航), Kai Wang(王凯), Jiaxing Yang(杨加兴), Chao Guan(关超), Hua Long(龙华), and Peixiang Lu(陆培祥)
    2023 (10):  107803-107803.  doi: 10.1088/1674-1056/acdc13
    摘要 ( 149 )   HTML ( 1 )   PDF(3015KB) ( 234 )  
    The generation characteristics of nonlinear optical signals and their multi-dimensional modulation at micro-nano scale have become a prominent research area in nanophotonics, and also the key to developing various novel nonlinear photonics devices. In recent years, the demand for higher nonlinear conversion efficiency and device integration has led to the rapid progress of hybrid nonlinear metasurfaces composed of nanostructures and nonlinear materials. As a joint platform of stable wavefront modulation, nonlinear metasurface and efficient frequency conversion, hybrid nonlinear metasurfaces offer a splendid opportunity for developing the next-generation of multipurpose flat-optics devices. This article provides a comprehensive review of recent advances in hybrid nonlinear metasurfaces for light-field modulation. The advantages of hybrid systems are discussed from the perspectives of multifunctional light-field modulation, valleytronic modulation, and quantum technologies. Finally, the remaining challenges of hybrid metasurfaces are summarized and future developments are also prospected.
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    Fully relativistic many-body perturbation energies, transition properties, and lifetimes of lithium-like iron Fe XXIV
    Shuang Li(李双), Min Zhao(赵敏), Guo-Qing Liu(刘国庆), Chang-Bao Hu(胡昌宝), and Guo-Zhu Pan(潘国柱)
    2023 (10):  103101-103101.  doi: 10.1088/1674-1056/acef01
    摘要 ( 167 )   HTML ( 1 )   PDF(630KB) ( 101 )  
    Employing the advanced relativistic configuration interaction (RCI) combined with the many-body perturbation theory (RMBPT) method, we report energies and lifetime values for the lowest 35 energy levels from the (1s$^2$)$nl$ configurations (where the principal quantum number $n = 2$-6 and the angular quantum number $l = 0,\ldots,n-1$) of lithium-like iron Fe XXIV, as well as complete data on the transition wavelengths, radiative rates, absorption oscillator strengths, and line strengths between the levels. Both the allowed (E1) and forbidden (magnetic dipole M1, magnetic quadrupole M2, and electric quadrupole E2) ones are reported. Through detailed comparisons with previous results, we assess the overall accuracies of present RMBPT results to be likely the most precise ones to date. Configuration interaction effects are found to be very important for the energies and radiative properties for the ion. The present RMBPT results are valuable for spectral line identification, plasma modeling, and diagnosing.
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    High efficient Raman sideband cooling and strong three-body recombination of atoms
    Yuqing Li(李玉清), Zhennan Liu(刘震南), Yunfei Wang(王云飞), Jizhou Wu(武寄洲), Wenliang Liu(刘文良), Yongming Fu(付永明), Peng Li(李鹏), Jie Ma(马杰), Liantuan Xiao(肖连团), and Suotang Jia(贾锁堂)
    2023 (10):  103701-103701.  doi: 10.1088/1674-1056/acec42
    摘要 ( 257 )   HTML ( 3 )   PDF(850KB) ( 236 )  
    We report a highly efficient three-dimensional degenerated Raman sideband cooling (3D dRSC) that enhances the loading of a magnetically levitated optical dipole trap, and observe the strong atom loss due to the three-body recombination. The 3D dRSC is implemented to obtain 5×107 Cs atoms with the temperature of ~ 480 nK. The cold temperature enables 1.8×107 atoms loaded into a crossed dipole trap with an optimized excessive levitation magnetic gradient. Compared to the loading of atoms from a bare magneto-optical trap or the gray-molasses cooling, there is a significant increase in the number of atoms loaded into the optical dipole trap. We derive for the three-body recombination coefficient of L3 = 7.73×10-25 cm6/s by analyzing the strong atom loss at a large scattering length of 1418 Bohr radius, and discover the transition from the strong three-body loss to the dominant one-body loss. Our result indicates that the lifetime of atoms in the optical dipole trap is finally decided by the one-body loss after the initial strong three-body loss.
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    Intruder trajectory tracking in a three-dimensional vibration-driven granular system: Unveiling the mechanism of the Brazil nut effect
    Tuo Li(李拓), Ke Cheng(程可), Zheng Peng(彭政), Hui Yang(杨晖), and Meiying Hou(厚美瑛)
    2023 (10):  104501-104501.  doi: 10.1088/1674-1056/acf040
    摘要 ( 235 )   HTML ( 3 )   PDF(2033KB) ( 249 )  
    We employ a Hall-effect magnetic sensor array to accurately track the trajectory of a single magnetic sphere, referred to as the "intruder," within a three-dimensional vibro-fluidized granular bed to unravel the underlying physical mechanism governing the motion of the intruder. Within the acceleration range of $3.5 {g}\ge \varGamma \ge 1.5 {g}$, we find that, regardless of the intruder's initial position, it consistently reaches the same equilibrium depth when the vibration acceleration ($\varGamma )$ and frequency ($\omega $) are fixed. For $\varGamma \le 2.5 {g}$, the equilibrium position lies on the surface of the granular bed, while for $\varGamma >2.5 {g}$, it shifts below the surface. Additionally, intruders with different densities exhibit varying equilibrium depths, with higher density resulting in a deeper equilibrium position. To understand the mechanism behind the intruder's upward or downward motion, we measure its rising or sinking velocities under different vibration parameters. Our findings demonstrate that the rising velocity of the intruder, under varying vibration accelerations ($\varGamma $) and frequencies ($\omega$), can be collapsed using the ratio $\varGamma /\omega $, while the sinking velocity remains unaffected by the vibration strength. This confirms that the upward motion of the larger sphere, associated with the Brazil nut effect, primarily arises from the void-filling mechanism of the bed particles. Furthermore, our experiments reveal that the presence of convection within the bed particles has minimal impact on the motion of the intruder.
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    Phonon dichroism in proximitized graphene
    Wen-Yu Shan(单文语)
    2023 (10):  106301-106301.  doi: 10.1088/1674-1056/acf207
    摘要 ( 213 )   HTML ( 1 )   PDF(1868KB) ( 239 )  
    We systematically investigate the phonon dichroism in proximitized graphene with broken time-reversal symmetry. We find that in the absence of any type of spin-orbit coupling, phonon dichroism vanishes. Linear and circular phonon dichroism occur in the presence of uniform (staggered) intrinsic spin-orbit coupling and ferromagnetic (antiferromagnetic) exchange coupling. All these situations can be distinguished by their specific behaviors of phonon absorption at the transition point. Our finding provides new possibilities to use phonon dichroism to identify the form of spin-orbit coupling and exchange coupling in proximitized graphene on various magnetic substrates.
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    Melting of electronic/excitonic crystals in 2D semiconductor moiré patterns: A perspective from the Lindemann criterion
    Jiyong Zhou(周纪勇), Jianju Tang(唐剑炬), and Hongyi Yu(俞弘毅)
    2023 (10):  107308-107308.  doi: 10.1088/1674-1056/acea6c
    摘要 ( 248 )   HTML ( 1 )   PDF(2853KB) ( 218 )  
    Using the Lindemann criterion, we analyzed the quantum and thermal melting of electronic/excitonic crystals recently discovered in two-dimensional (2D) semiconductor moiré patterns. We show that the finite 2D screening of the atomically thin material can suppress (enhance) the inter-site Coulomb (dipolar) interaction strength, thus inhibits (facilitates) the formation of the electronic (excitonic) crystal. Meanwhile, a strong enough moiré confinement is found to be essential for realizing the crystal phase with a wavelength near 10 nm or shorter. From the calculated Lindemann ratio which quantifies the fluctuation of the site displacement, we estimate that the crystal will melt into a liquid above a critical temperature ranging from several tens Kelvin to above 100 K (depending on the system parameters).
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    Lower bound on the spread of valley splitting in Si/SiGe quantum wells induced by atomic rearrangement at the interface
    Gang Wang(王刚), Shan Guan(管闪), Zhi-Gang Song(宋志刚), and Jun-Wei Luo(骆军委)
    2023 (10):  107309-107309.  doi: 10.1088/1674-1056/acf208
    摘要 ( 184 )   HTML ( 2 )   PDF(1455KB) ( 171 )  
    The achievement of universal quantum computing critically relies on scalability. However, ensuring the necessary uniformity for scalable silicon electron spin qubits poses a significant challenge due to the considerable fluctuations in valley splitting energy ($E_{\textrm{VS}}$) across quantum dot arrays, which impede the initialization of qubit systems comprising multiple spins and give rise to spin-valley entanglement resulting in the loss of spin information. These $E_{\textrm{VS}}$ fluctuations have been attributed to variations in the in-plane averaged alloy concentration along the confinement direction of Si/SiGe quantum wells. In this study, employing atomistic pseudopotential calculations, we unveil a significant spectrum of $E_{\textrm{VS}}$ even in the absence of such concentration fluctuations. This spectrum represents the lower limit of the wide range of $E_{\textrm{VS}}$ observed in numerous Si/SiGe quantum devices. By constructing simplified interface atomic step models, we analytically demonstrate that the lower bound of the $E_{\textrm{VS}}$ spread originates from the in-plane random distribution of Si and Ge atoms within SiGe barriers — an inherent characteristic that has been previously overlooked. Additionally, we propose an interface engineering approach to mitigate the in-plane randomness-induced fluctuations in $E_{\textrm{VS}}$ by inserting a few monolayers of pure Ge barrier at the Si/SiGe interface. Our findings provide valuable insights into the critical role of in-plane randomness in determining $E_{\textrm{VS}}$ in Si/SiGe quantum devices and offer reliable methods to enhance the feasibility of scalable Si-based spin qubits.
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    Spin-orbit torque in perpendicularly magnetized [Pt/Ni] multilayers
    Ying Cao(曹颖), Zhicheng Xie(谢志成), Zhiyuan Zhao(赵治源), Yumin Yang(杨雨民), Na Lei(雷娜), Bingfeng Miao(缪冰锋), and Dahai Wei(魏大海)
    2023 (10):  107507-107507.  doi: 10.1088/1674-1056/acee57
    摘要 ( 198 )   HTML ( 2 )   PDF(1116KB) ( 185 )  
    The performance of spin-orbit torque (SOT) in heavy metal/ferromagnetic metal periodic multilayers has attracted widespread attention. In this paper, we have successfully fabricated a series of perpendicular magnetized [Pt($2-t$)/Ni($t$)]$_{4}$ multilayers, and studied the SOT in the multilayers by varying the thickness of Ni layer $t$. The current induced magnetization switching was achieved with a critical current density of 1$\times10^{7}$ A/cm$^{2}$. The damping-like SOT efficiency $\xi_{\rm DL}$ was extracted from an extended harmonic Hall measurement. We demonstrated that the $\xi_{\rm DL}$ can be effectively modulated by $t_{\mathrm{Pt}}/t_{\mathrm{Ni}}$ ratio of Pt and Ni in the multilayers. The SOT investigation about the [Pt/Ni]$_{N}$ multilayers might provide new material candidates for practical perpendicular SOT-MRAM devices.
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    Rubidium-induced phase transitions among metallic, band-insulating, Mott-insulating phases in 1T-TaS2
    Zhengguo Wang(王政国), Weiliang Yao(姚伟良), Yudi Wang(王宇迪), Ziming Xin(信子鸣), Tingting Han(韩婷婷), Lei Chen(陈磊), Yi Ou(欧仪), Yu Zhu(朱玉), Cong Cai(蔡淙), Yuan Li(李源), and Yan Zhang(张焱)
    2023 (10):  107404-107404.  doi: 10.1088/1674-1056/acec40
    摘要 ( 312 )   HTML ( 1 )   PDF(1605KB) ( 344 )  
    Realizing phase transitions via non-thermal sample manipulations is important not only for applications, but also for uncovering the underlying physics. Here, we report on the discovery of two distinct metal-insulator transitions in 1T-TaS2 via angle-resolved photoemission spectroscopy and in-situ rubidium deposition. At 205 K, the rubidium deposition drives a normal metal-insulator transition via filling electrons into the conduction band. While at 225 K, however, the rubidium deposition drives a bandwidth-controlled Mott transition as characterized by a rapid collapsing of Mott gap and a loss of spectral weight of the lower Hubbard band. Our result, from a doping-controlled perspective, succeeds in distinguishing the metallic, band-insulating, and Mott-insulating phases of 1T-TaS2, manifesting a delicate balance among the electron-itineracy, interlayer-coupling and Coulomb repulsion. We also establish an effective method to tune the balance between these interactions, which is useful in seeking exotic electronic phases and designing functional phase-changing devices.
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    Nonlinear three-magnon scattering in low-damping La0.67Sr0.33MnO3 thin films
    Yuelin Zhang(张跃林), Lutong Sheng(盛路通), Jilei Chen(陈济雷), Jie Wang(王婕), Zengtai Zhu(朱增泰), Rundong Yuan(袁润东), Jingdi Lu(鲁京迪), Hanchen Wang(王涵晨), Sijie Hao(郝思洁), Peng Chen(陈鹏), Guoqiang Yu(于国强), Xiufeng Han(韩秀峰), and Haiming Yu(于海明)
    2023 (10):  107505-107505.  doi: 10.1088/1674-1056/acedf8
    摘要 ( 185 )   HTML ( 1 )   PDF(1546KB) ( 161 )  
    Three-magnon scattering, a nonlinear process in which a high-energy magnon splits into two low-energy magnons with energy and momentum conservation, has been widely studied in the magnonics community. Here, we report experimental observation of nonlinear three-magnon scattering in La0.67Sr0.33MnO3 thin films with low magnetic damping (~ 10-4) by all-electric and angle-resolved spin wave spectroscopy. The reflection spectra of the spin wave resonance with high-power excitation at Damon-Eshbach configuration demonstrate a scattering regime with gradual signal disappearance, where a magnon of Damon-Eshbach mode decays into two magnons of volume mode above the threshold power (-10 dBm) of the injected microwave. The nonlinear scattering is only allowed at low-field regime and the calculated dispersions of dipole-exchange spin wave claim the mechanism of allowed and forbidden three-magnon scattering. The films and heterostructures of La0.67Sr0.33MnO3 have been already demonstrated with rich physical phenomena and great versatility, in this work the nonlinear magnetic dynamics of La0.67Sr0.33MnO3 thin films is revealed, which offer more possibility for applications to oxide magnonics and nonlinear magnonic devices.
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    Activated dissociation of H2 on the Cu(001) surface: The role of quantum tunneling
    Xiaofan Yu(于小凡), Yangwu Tong(童洋武), and Yong Yang(杨勇)
    2023 (10):  108103-108103.  doi: 10.1088/1674-1056/acd2b3
    摘要 ( 162 )   HTML ( 0 )   PDF(4151KB) ( 146 )  
    The activation and dissociation of hydrogen molecules (H2) on the Cu(001) surface are studied theoretically. Using first-principles calculations, the activation barrier for the dissociation of H2 on Cu(001) is determined to be ~ 0.59 eV in height. It is found that the electron transfer from the copper substrate to H2 plays a key role in the activation and breaking of the H-H bond, and the formation of the Cu-H bonds. Two stationary states are identified at around the critical height of bond breaking, corresponding to the molecular and the dissociative states, respectively. Using the transfer matrix method, we also investigate the role of quantum tunneling in the dissociation process along the minimum energy pathway (MEP), which is found to be significant at or below room temperature. At a given temperature, the tunneling contributions due to the translational and the vibrational motions of H2 are quantified for the dissociation process. Within a wide range of temperature, the effects of quantum tunneling on the effective barriers of dissociation and the rate constants are observed. The deduced energetic parameters associated with the thermal equilibrium and non-equilibrium (molecular beam) conditions are comparable to experimental data. In the low-temperature region, the crossover from classical to quantum regime is identified.
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    Trajectory equation of a lump before and after collision with other waves for generalized Hirota-Satsuma-Ito equation
    Yarong Xia(夏亚荣), Kaikai Zhang(张开开), Ruoxia Yao(姚若侠), and Yali Shen(申亚丽)
    2023 (10):  100201-100201.  doi: 10.1088/1674-1056/acd62c
    摘要 ( 158 )   HTML ( 1 )   PDF(1861KB) ( 81 )  
    Based on the Hirota bilinear and long wave limit methods, the hybrid solutions of $m$-lump with $n$-soliton and $n$-breather wave for generalized Hirota-Satsuma-Ito (GHSI) equation are constructed. Then, by approximating solutions of the GHSI equation along some parallel orbits at infinity, the trajectory equation of a lump wave before and after collisions with $n$-soliton and $n$-breather wave are studied, and the expressions of phase shift for lump wave before and after collisions are given. Furthermore, it is revealed that collisions between the lump wave and other waves are elastic, the corresponding collision diagrams are used to further explain.
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    Effect of conformity on evolution of cooperation in a coordination game
    Xianjia Wang(王先甲) and Tao Wang(王饕)
    2023 (10):  100202-100202.  doi: 10.1088/1674-1056/acd9c2
    摘要 ( 139 )   HTML ( 0 )   PDF(4446KB) ( 35 )  
    Individual decision-making processes are not solely driven by self-interest maximization but are also influenced by the pressure to conform to the group. In primary games like the prisoner's dilemma, the presence of conformity pressure may facilitate the constructive development of cooperative behavior. In this study, we investigate how conformity influences the growth of cooperation in complicated coordination games. Our findings reveal that, even in the presence of stringent game rules, conformity can promote cooperation. In fact, a certain level of conformity pressure can even eliminate the "defection basin" of deer hunting games played on regular networks. Additionally, we demonstrate that the effect of conformity on cooperative behavior is contingent upon the degree of conformity pressure, with different levels of conformity pressure producing opposite effects. These findings provide novel insights into the promotion of cooperative evolution. For instance, if increasing the reward for cooperation has proven ineffective, manipulating the proportion of initial strategy choices may be a more promising approach.
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    Geometric discord of tripartite quantum systems
    Chunhe Xiong(熊春河), Wentao Qi(齐文韬), Maoke Miao(缪茂可), and Minghui Wu(吴明晖)
    2023 (10):  100301-100301.  doi: 10.1088/1674-1056/acdc11
    摘要 ( 147 )   HTML ( 0 )   PDF(545KB) ( 131 )  
    We study the quantification of geometric discord for tripartite quantum systems. Firstly, we obtain the analytic formula of geometric discord for tripartite pure states. It is already known that the geometric discord of pure states reduces to the geometric entanglement in bipartite systems, the results presented here show that this property is no longer true in tripartite systems. Furthermore, we provide an operational meaning for tripartite geometric discord by linking it to quantum state discrimination, that is, we prove that the geometric discord of tripartite states is equal to the minimum error probability to discriminate a set of quantum states with von Neumann measurement. Lastly, we calculate the geometric discord of three-qubit Bell diagonal states and then investigate the dynamic behavior of tripartite geometric discord under local decoherence. It is interesting that the frozen phenomenon exists for geometric discord in this scenario.
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    Broadband multi-channel quantum noise suppression and phase-sensitive modulation based on entangled beam
    Ke Di(邸克), Shuai Tan(谈帅), Anyu Cheng(程安宇), Yu Liu(刘宇), and Jiajia Du(杜佳佳)
    2023 (10):  100302-100302.  doi: 10.1088/1674-1056/acd8a8
    摘要 ( 151 )   HTML ( 0 )   PDF(2537KB) ( 59 )  
    We present a theoretical scheme for broadband multi-channel quantum noise suppression and phase-sensitive modulation of continuous variables in a coupled resonant system with quantum entanglement properties. The effects of different coupling strengths, pumping power in suppressing quantum noise and controlling the width of quantum interference channels are analyzed carefully. Furthermore, quantum noise suppression at quadrature amplitude is obtained with phase-sensitive modulation. It shows that the entanglement strength of the output field and the quantum noise suppression effect can be enhanced significantly by a strong pumping filed due to interaction of pumping light with the nonlinear crystal. The full width at half maxima (FWHM) of the noise curve at the resonant peak ($\varDelta$ =0 MHz) is broadened up to 2.17 times compared to the single cavity. In the strong coupling resonant system, the FWHM at $\varDelta$ =0 MHz ($\varDelta$ =±3.1 MHz) is also broadened up to 1.27 (3.53) times compared to the weak coupling resonant system case. The multi-channel quantum interference creates an electromagnetically induced transparent-like line shape, which can be used to improve the transmission efficiency and stability of wave packets in quantum information processing and quantum memory.
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    Effects of quantum quench on entanglement dynamics in antiferromagnetic Ising model
    Yue Li(李玥), Panpan Fang(房盼盼), Zhe Wang(王哲), Panpan Zhang(张盼盼), Yuliang Xu(徐玉良), and Xiangmu Kong(孔祥木)
    2023 (10):  100303-100303.  doi: 10.1088/1674-1056/ace15c
    摘要 ( 155 )   HTML ( 0 )   PDF(774KB) ( 83 )  
    We study the relationship between quench dynamics of entanglement and quantum phase transition in the antiferromagnetic Ising model with the Dzyaloshinskii-Moriya (DM) interaction by using the quantum renormalization-group method and the definition of negativity. Two types of quench protocols (i) adding the DM interaction suddenly and (ii) rotating the spins around x axis are considered to drive the dynamics of the system, respectively. By comparing the behaviors of entanglement in both types of quench protocols, the effects of quench on dynamics of entanglement are studied. It is found that there is the same characteristic time at which the negativity firstly reaches its maximum although the system shows different dynamical behaviors. Especially, the characteristic time can accurately reflect the quantum phase transition from antiferromagnetic to saturated chiral phases in the system. In addition, the correlation length exponent can be obtained by exploring the nonanalytic and scaling behaviors of the derivative of the characteristic time.
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    Realization of high-fidelity and robust geometric gates with time-optimal control technique in superconducting quantum circuit
    Zhimin Wang(王治旻), Zhuang Ma(马壮), Xiangmin Yu(喻祥敏), Wen Zheng(郑文), Kun Zhou(周坤), Yujia Zhang(张宇佳), Yu Zhang(张钰), Dong Lan(兰栋), Jie Zhao(赵杰), Xinsheng Tan(谭新生), Shaoxiong Li(李邵雄), and Yang Yu(于扬)
    2023 (10):  100304-100304.  doi: 10.1088/1674-1056/ace15b
    摘要 ( 182 )   HTML ( 1 )   PDF(2785KB) ( 220 )  
    One of the key features required to realize fault-tolerant quantum computation is the robustness of quantum gates against errors. Since geometric quantum gate is naturally insensitivity to noise, it appears to be a promising routine to achieve high-fidelity, robust quantum gates. The implementation of geometric quantum gate however faces some troubles such as its complex interaction among multiple energy levels. Moreover, traditional geometric schemes usually take more time than equivalent dynamical ones. Here, we experimentally demonstrate a geometric gate scheme with the time-optimal control (TOC) technique in a superconducting quantum circuit. With a transmon qubit and operations restricted to two computational levels, we implement a set of geometric gates which exhibit better robustness features against control errors than the dynamical counterparts. The measured fidelities of TOC $X$ gate and ${X}/{2}$ gate are $99.81 \%$ and $99.79 \%$ respectively. Our work shows a promising routine toward scalable fault-tolerant quantum computation.
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    Visualizing and witnessing first-order coherence, Bell nonlocality and purity by using a quantum steering ellipsoid in the non-inertial frame
    Huan Yang(杨欢), Ling-Ling Xing(邢玲玲), Ming-Ming Du(杜明明), Min Kong(孔敏), Gang Zhang(张刚), and Liu Ye(叶柳)
    2023 (10):  100305-100305.  doi: 10.1088/1674-1056/acb762
    摘要 ( 303 )   HTML ( 0 )   PDF(3227KB) ( 230 )  
    A quantum steering ellipsoid (QSE) is a visual characterization for bipartite qubit systems, and it is also a novel avenue for describing and detecting quantum correlations. Herein, by using a QSE, we visualize and witness the first-order coherence (FOC), Bell nonlocality (BN) and purity under non-inertial frames. Also, the collective influences of the depolarizing channel and the non-coherence-generating channel (NCGC) on the FOC, BN and purity are investigated in the QSE formalism. The results reveal that the distance from the center of the QSE to the center of the Bloch sphere visualizes the FOC of a bipartite system, the lengths of the QSE semiaxis visualize the BN, and the QSE's shape and position dominate the purity of the system. One can capture the FOC, BN and purity via the shape and position of the QSE in the non-inertial frame. The depolarizing channel (the NCGC) gives rise to the shrinking and degradation (the periodical oscillation) of the QSE. One can use these traits to visually characterize and detect the FOC, BN and purity under the influence of external noise. Of particular note is that the condition for the QSE to achieve the center of the Bloch sphere cannot be influenced by the depolarizing channel and the NCGC. The characterization shows that the conditions for the disappearance of the FOC are invariant under the additional influences of the depolarizing channel and NCGC.
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    A backdoor attack against quantum neural networks with limited information
    Chen-Yi Huang(黄晨猗) and Shi-Bin Zhang(张仕斌)
    2023 (10):  100306-100306.  doi: 10.1088/1674-1056/acd8ab
    摘要 ( 146 )   HTML ( 0 )   PDF(906KB) ( 68 )  
    Backdoor attacks are emerging security threats to deep neural networks. In these attacks, adversaries manipulate the network by constructing training samples embedded with backdoor triggers. The backdoored model performs as expected on clean test samples but consistently misclassifies samples containing the backdoor trigger as a specific target label. While quantum neural networks (QNNs) have shown promise in surpassing their classical counterparts in certain machine learning tasks, they are also susceptible to backdoor attacks. However, current attacks on QNNs are constrained by the adversary's understanding of the model structure and specific encoding methods. Given the diversity of encoding methods and model structures in QNNs, the effectiveness of such backdoor attacks remains uncertain. In this paper, we propose an algorithm that leverages dataset-based optimization to initiate backdoor attacks. A malicious adversary can embed backdoor triggers into a QNN model by poisoning only a small portion of the data. The victim QNN maintains high accuracy on clean test samples without the trigger but outputs the target label set by the adversary when predicting samples with the trigger. Furthermore, our proposed attack cannot be easily resisted by existing backdoor detection methods.
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    Approximate error correction scheme for three-dimensional surface codes based reinforcement learning
    Ying-Jie Qu(曲英杰), Zhao Chen(陈钊), Wei-Jie Wang(王伟杰), and Hong-Yang Ma(马鸿洋)
    2023 (10):  100307-100307.  doi: 10.1088/1674-1056/acd8a9
    摘要 ( 194 )   HTML ( 0 )   PDF(1531KB) ( 77 )  
    Quantum error correction technology is an important method to eliminate errors during the operation of quantum computers. In order to solve the problem of influence of errors on physical qubits, we propose an approximate error correction scheme that performs dimension mapping operations on surface codes. This error correction scheme utilizes the topological properties of error correction codes to map the surface code dimension to three dimensions. Compared to previous error correction schemes, the present three-dimensional surface code exhibits good scalability due to its higher redundancy and more efficient error correction capabilities. By reducing the number of ancilla qubits required for error correction, this approach achieves savings in measurement space and reduces resource consumption costs. In order to improve the decoding efficiency and solve the problem of the correlation between the surface code stabilizer and the 3D space after dimension mapping, we employ a reinforcement learning (RL) decoder based on deep $Q$-learning, which enables faster identification of the optimal syndrome and achieves better thresholds through conditional optimization. Compared to the minimum weight perfect matching decoding, the threshold of the RL trained model reaches 0.78%, which is 56% higher and enables large-scale fault-tolerant quantum computation.
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    Single-qubit quantum classifier based on gradient-free optimization algorithm
    Anqi Zhang(张安琪), Kelun Wang(王可伦), Yihua Wu(吴逸华), and Sheng-Mei Zhao(赵生妹)
    2023 (10):  100308-100308.  doi: 10.1088/1674-1056/acb75e
    摘要 ( 147 )   HTML ( 0 )   PDF(691KB) ( 29 )  
    A single-qubit quantum classifier (SQC) based on a gradient-free optimization (GFO) algorithm, named the GFO-based SQC, is proposed to overcome the effects of barren plateaus caused by quantum devices. Here, a rotation gate $R_{X}(\phi)$ is applied on the single-qubit binary quantum classifier, and the training data and parameters are loaded into $\phi$ in the form of vector multiplication. The cost function is decreased by finding the value of each parameter that yields the minimum expectation value of measuring the quantum circuit. The algorithm is performed iteratively for all parameters one by one until the cost function satisfies the stop condition. The proposed GFO-based SQC is demonstrated for classification tasks in Iris and MNIST datasets and compared with the Adam-based SQC and the quantum support vector machine (QSVM). Furthermore, the performance of the GFO-based SQC is discussed when the rotation gate in the quantum device is under different types of noise. The simulation results show that the GFO-based SQC can reach a high accuracy in reduced time. Additionally, the proposed GFO algorithm can quickly complete the training process of the SQC. Importantly, the GFO-based SQC has a good performance in noisy environments.
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    A quantum algorithm for Toeplitz matrix-vector multiplication
    Shang Gao(高尚) and Yu-Guang Yang(杨宇光)
    2023 (10):  100309-100309.  doi: 10.1088/1674-1056/acb914
    摘要 ( 188 )   HTML ( 0 )   PDF(511KB) ( 82 )  
    Toeplitz matrix-vector multiplication is widely used in various fields, including optimal control, systolic finite field multipliers, multidimensional convolution, etc. In this paper, we first present a non-asymptotic quantum algorithm for Toeplitz matrix-vector multiplication with time complexity ${\cal O}(\kappa \mathrm{polylog}n)$, where $\kappa $ and $2n$ are the condition number and the dimension of the circulant matrix extended from the Toeplitz matrix, respectively. For the case with an unknown generating function, we also give a corresponding non-asymptotic quantum version that eliminates the dependency on the $L_{1}$-norm $\varrho $ of the displacement of the structured matrices. Due to the good use of the special properties of Toeplitz matrices, the proposed quantum algorithms are sufficiently accurate and efficient compared to the existing quantum algorithms under certain circumstances.
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    Mode dynamics of Bose-Einstein condensates in a single-well potential
    Yaojun Ying(应耀俊), Lizhen Sun(孙李真), and Haibin Li(李海彬)
    2023 (10):  100310-100310.  doi: 10.1088/1674-1056/acdedb
    摘要 ( 137 )   HTML ( 0 )   PDF(2158KB) ( 30 )  
    We investigate dynamics of Bose-Einstein condensates (BECs) in a single-well potential using the mode-coupling method. Symmetry is shown to play a key role in the coupling between modes. A proper mode-coupling theory of the dynamics of BECs in a single-well potential should include at least four modes. In this context, the ideal BEC system can be decomposed into two independent subsystems when the coupling is caused by external potential perturbation and is linear. The mode dynamics of non-ideal BECs with interaction shows rich behavior. The combination of nonlinear coupling and initial condition leads to the different regimes of mode dynamics, from regularity to non-regularity, which also indicates a change of the dependence of coupling on the symmetry of modes.
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    Non-Gaussian approach: Withstanding loss and noise of multi-scattering underwater channel for continuous-variable quantum teleportation
    Hao Wu(吴昊), Hang Zhang(张航), Yiwu Zhu(朱益武), Gaofeng Luo(罗高峰), Zhiyue Zuo(左峙岳), Xinchao Ruan(阮新朝), and Ying Guo(郭迎)
    2023 (10):  100311-100311.  doi: 10.1088/1674-1056/ace681
    摘要 ( 113 )   HTML ( 0 )   PDF(5790KB) ( 60 )  
    Underwater quantum communication plays a crucial role in ensuring secure data transmission and extensible quantum networks in underwater environments. However, the implementation of such applications encounters challenges due to the light attenuation caused by the complicated natural seawater. This paper focuses on employing a model based on seawater chlorophyll-a concentration to characterize the absorption and scattering of light through quantum channels. We propose a multi-scattering random channel model, which demonstrates characteristics of the excess noise in different propagation directions of communication links. Furthermore, we consider the fidelity of a continuous-variable quantum teleportation through seawater channel. To enhance transmission performance, non-Gaussian operations have been conducted. Numerical simulations show that incorporating non-Gaussian operations enables the protocol to achieve higher fidelity transmission or lower fidelity fading rates over longer transmission distances.
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    Detection of healthy and pathological heartbeat dynamics in ECG signals using multivariate recurrence networks with multiple scale factors
    Lu Ma(马璐), Meihui Chen(陈梅辉), Aijun He(何爱军), Deqiang Cheng(程德强), and Xiaodong Yang(杨小冬)
    2023 (10):  100501-100501.  doi: 10.1088/1674-1056/acb422
    摘要 ( 124 )   HTML ( 0 )   PDF(3297KB) ( 37 )  
    The electrocardiogram (ECG) is one of the physiological signals applied in medical clinics to determine health status. The physiological complexity of the cardiac system is related to age, disease, etc. For the investigation of the effects of age and cardiovascular disease on the cardiac system, we then construct multivariate recurrence networks with multiple scale factors from multivariate time series. We propose a new concept of cross-clustering coefficient entropy to construct a weighted network, and calculate the average weighted path length and the graph energy of the weighted network to quantitatively probe the topological properties. The obtained results suggest that these two network measures show distinct changes between different subjects. This is because, with aging or cardiovascular disease, a reduction in the conductivity or structural changes in the myocardium of the heart contributes to a reduction in the complexity of the cardiac system. Consequently, the complexity of the cardiac system is reduced. After that, the support vector machine (SVM) classifier is adopted to evaluate the performance of the proposed approach. Accuracy of 94.1% and 95.58% between healthy and myocardial infarction is achieved on two datasets. Therefore, this method can be adopted for the development of a noninvasive and low-cost clinical prognostic system to identify heart-related diseases and detect hidden state changes in the cardiac system.
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    Dynamic decision and its complex dynamics analysis of low-carbon supply chain considering risk-aversion under carbon tax policy
    Jin-Chai Lin(林金钗), Ru-Guo Fan(范如国), Yuan-Yuan Wang(王圆缘), and Kang Du(杜康)
    2023 (10):  100502-100502.  doi: 10.1088/1674-1056/acd2b5
    摘要 ( 142 )   HTML ( 0 )   PDF(4760KB) ( 49 )  
    This study establishes a low-carbon supply chain game model under the centralized decision situation and the decentralized decision situation considering the manufacturer risk-aversion behavior, and discusses the influence of the manufacturer risk-aversion behavior on the optimal decision, profit, coordination, and complex dynamics of the supply chain. We find that comparing with the risk-neutral decentralized decision, the increase of manufacturer's risk tolerance attitude can narrow the gap between the supply chain profit and the centralized decision, but it will further reduce the carbon emission reduction level. The increase of risk tolerance of the manufacturer and carbon tax will narrow the stable region of the system. Under this situation, the manufacturer should carefully adjust parameters to prevent the system from losing stability, especially the adjustment parameters for carbon emission reduction level. When the system is in a chaotic state, the increase of carbon tax rate makes the system show more complex dynamic characteristics. Under the chaotic state, it is difficult for the manufacturer to make correct price decision and carbon emission reduction strategy for the next period, which damages its profit, but increases the profit of the retailer and the supply chain. Finally, the carbon emission reduction cost-sharing contract is proposed to improve the carbon emission reduction level and the supply chain efficiency, achieving Pareto improvement. The stability region of the system is larger than that in the centralized decision situation, but the increase of the cost sharing coefficient will reduce the stability of the system in the decentralized decision-making situation.
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    Rucklidge-based memristive chaotic system: Dynamic analysis and image encryption
    Can-Ling Jian(蹇璨岭), Ze-An Tian(田泽安), Bo Liang(梁波), Chen-Yang Hu(胡晨阳), Qiao Wang(王桥), and Jing-Xi Chen(陈靖翕)
    2023 (10):  100503-100503.  doi: 10.1088/1674-1056/acdac3
    摘要 ( 160 )   HTML ( 0 )   PDF(6661KB) ( 66 )  
    A new four-dimensional (4D) memristive chaotic system is obtained by introducing a memristor into the Rucklidge chaotic system, and a detailed dynamic analysis of the system is performed. The sensitivity of the system to parameters allows it obtains 16 different attractors by changing only one parameter. The various transient behaviors and excellent spectral entropy and C0 complexity values of the system can also reflect the high complexity of the system. A circuit is designed and verified the feasibility of the system from the physical level. Finally, the system is applied to image encryption, and the security of the encryption system is analyzed from multiple aspects, providing a reference for the application of such memristive chaotic systems.
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    Bipolar-growth multi-wing attractors and diverse coexisting attractors in a new memristive chaotic system
    Wang-Peng Huang(黄旺鹏) and Qiang Lai(赖强)
    2023 (10):  100504-100504.  doi: 10.1088/1674-1056/ace1d9
    摘要 ( 147 )   HTML ( 1 )   PDF(4011KB) ( 101 )  
    This article proposes a non-ideal flux-controlled memristor with a bisymmetric sawtooth piecewise function, and a new multi-wing memristive chaotic system (MMCS) based on the memristor is generated. Compared with other existing MMCSs, the most eye-catching point of the proposed MMCS is that the amplitude of the wing will enlarge towards the poles as the number of wings increases. Diverse coexisting attractors are numerically found in the MMCS, including chaos, quasi-period, and stable point. The circuits of the proposed memristor and MMCS are designed and the obtained results demonstrate their validity and reliability.
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    Visibility graph approach to extreme event series
    Jing Zhang(张晶), Xiaolu Chen(陈晓露), Haiying Wang(王海英), Changgui Gu(顾长贵), and Huijie Yang(杨会杰)
    2023 (10):  100505-100505.  doi: 10.1088/1674-1056/acd62b
    摘要 ( 123 )   HTML ( 0 )   PDF(7010KB) ( 78 )  
    An extreme event may lead to serious disaster to a complex system. In an extreme event series there exist generally non-trivial patterns covering different time scales. Investigations on extreme events are currently based upon statistics, where the patterns are merged into averages. In this paper from extreme event series we constructed extreme value series and extreme interval series. And the visibility graph is then adopted to display the patterns formed by the increases/decreases of extreme value or interval faster/slower than the linear ones. For the fractional Brownian motions, the properties for the constructed networks are the persistence, threshold, and event-type-independent, $e.g.$, the degree distributions decay exponentially with almost identical speeds, the nodes cluster into modular structures with large and similar modularity degrees, and each specific network has a perfect hierarchical structure. For the volatilities of four stock markets (NSDQ, SZI, FTSE100, and HSI), the properties for the former three's networks are threshold- and market-independent. Comparing with the factional Brownian motions, their degree distributions decay exponentially but with slower speeds, their modularity behaviors are significant but with smaller modularity degrees. The fourth market behaves similar qualitatively but different quantitatively with the three markets. Interestingly, all the transition frequency networks share an identical backbone composed of nine edges and the linked graphlets. The universal behaviors give us a framework to describe extreme events from the viewpoint of network.
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    Distributed dynamic event-based finite-time dissipative synchronization control for semi-Markov switched fuzzy cyber-physical systems against random packet losses
    Xiru Wu(伍锡如), Yuchong Zhang(张煜翀), Tiantian Zhang(张畑畑), and Binlei Zhang(张斌磊)
    2023 (10):  100506-100506.  doi: 10.1088/1674-1056/acb91b
    摘要 ( 153 )   HTML ( 0 )   PDF(2223KB) ( 48 )  
    This paper is concerned with the finite-time dissipative synchronization control problem of semi-Markov switched cyber-physical systems in the presence of packet losses, which is constructed by the Takagi-Sugeno fuzzy model. To save the network communication burden, a distributed dynamic event-triggered mechanism is developed to restrain the information update. Besides, random packet dropouts following the Bernoulli distribution are assumed to occur in sensor to controller channels, where the triggered control input is analyzed via an equivalent method containing a new stochastic variable. By establishing the mode-dependent Lyapunov-Krasovskii functional with augmented terms, the finite-time boundness of the error system limited to strict dissipativity is studied. As a result of the help of an extended reciprocally convex matrix inequality technique, less conservative criteria in terms of linear matrix inequalities are deduced to calculate the desired control gains. Finally, two examples in regard to practical systems are provided to display the effectiveness of the proposed theory.
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    Explosive synchronization of multi-layer complex networks based on star connection between layers with delay
    Yan-Liang Jin(金彦亮), Qian-Yuan Han(韩钱源), Run-Zhu Guo(郭润珠), Yuan Gao(高塬), and Li-Quan Shen(沈礼权)
    2023 (10):  100507-100507.  doi: 10.1088/1674-1056/acbaf1
    摘要 ( 129 )   HTML ( 2 )   PDF(1087KB) ( 47 )  
    Explosive synchronization (ES) is a kind of first-order jump phenomenon that exists in physical and biological systems. In recent years, researchers have focused on ES between single-layer and multi-layer networks. Most research on complex networks with delay has focused on single-layer or double-layer networks, multi-layer networks are seldom explored. In this paper, we propose a Kuramoto model of frequency weights in multi-layer complex networks with delay and star connections between layers. Through theoretical analysis and numerical verification, the factors affecting the backward critical coupling strength are analyzed. The results show that the interaction between layers and the average node degree has a direct effect on the backward critical coupling strength of each layer network. The location of the delay, the size of the delay, the number of network layers, the number of nodes, and the network topology are revealed to have no direct impact on the backward critical coupling strength of the network. Delay is introduced to explore the influence of delay and other related parameters on ES.
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    Inatorial forecasting method considering macro and micro characteristics of chaotic traffic flow
    Yue Hou(侯越), Di Zhang(张迪), Da Li(李达), and Ping Yang(杨萍)
    2023 (10):  100508-100508.  doi: 10.1088/1674-1056/acd3df
    摘要 ( 207 )   HTML ( 1 )   PDF(981KB) ( 54 )  
    Traffic flow prediction is an effective strategy to assess traffic conditions and alleviate traffic congestion. Influenced by external non-stationary factors and road network structure, traffic flow sequences have macro spatiotemporal characteristics and micro chaotic characteristics. The key to improving the model prediction accuracy is to fully extract the macro and micro characteristics of traffic flow time sequences. However, traditional prediction model by only considers time features of traffic data, ignoring spatial characteristics and nonlinear characteristics of the data itself, resulting in poor model prediction performance. In view of this, this research proposes an intelligent combination prediction model taking into account the macro and micro features of chaotic traffic data. Firstly, to address the problem of time-consuming and inefficient multivariate phase space reconstruction by iterating nodes one by one, an improved multivariate phase space reconstruction method is proposed by filtering global representative nodes to effectively realize the high-dimensional mapping of chaotic traffic flow. Secondly, to address the problem that the traditional combinatorial model is difficult to adequately learn the macro and micro characteristics of chaotic traffic data, a combination of convolutional neural network (CNN) and convolutional long short-term memory (ConvLSTM) is utilized for capturing nonlinear features of traffic flow more comprehensively. Finally, to overcome the challenge that the combined model performance degrades due to subjective empirical determined network parameters, an improved lightweight particle swarm is proposed for improving prediction accuracy by optimizing model hyperparameters. In this paper, two highway datasets collected by the Caltrans Performance Measurement System (PeMS) are taken as the research objects, and the experimental results from multiple perspectives show that the comprehensive performance of the method proposed in this research is superior to those of the prevalent methods.
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    High-order effect on the transmission of two optical solitons
    Houhui Yi(伊厚会), Yanli Yao(姚延立), Xin Zhang(张鑫), and Guoli Ma(马国利)
    2023 (10):  100509-100509.  doi: 10.1088/1674-1056/aceeec
    摘要 ( 147 )   HTML ( 0 )   PDF(1362KB) ( 128 )  
    For optical solitons with the pulse width in the subpicosecond and femtosecond scales in optical fibers, a modified model containing higher-order effects such as third-order dispersion and third-order nonlinearity is needed. In this paper, in order to study the dynamic mechanism of femtosecond solitons in different media, we take the nonlinear Schrödinger equation considering higher-order effects as the theoretical model, discuss the propagation of solitons in single-mode fibers, and explore the third-order dispersion and third-order nonlinear effects on the generation of optical solitons. The exact solution of the theoretical model is obtained through the bilinear method, and the transmission characteristics of two solitons with exact soliton solutions in actual fiber systems are analyzed and studied. The influence of various conditions on the transmission and interaction of optical solitons is explored. Methods for optimizing the transmission characteristics of optical solitons in optical communication systems are suggested. The relevant conclusions of this paper have guiding significance for improving the quality of fiber optic communication and increasing bit rates.
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    Simulation research on surface growth process of positive and negative frequency detuning chromium atom lithographic gratings
    Zhi-Jun Yin(尹志珺), Zhao-Hui Tang(唐朝辉), Wen Tan(谭文), Guang-Xu Xiao(肖光旭), Yu-Lin Yao(姚玉林), Dong-Bai Xue(薛栋柏), Zhen-Jie Gu(顾振杰), Li-Hua Lei(雷李华), Xiong Dun(顿雄), Xiao Deng(邓晓), Xin-Bin Cheng(程鑫彬), and Tong-Bao Li(李同保)
    2023 (10):  100601-100601.  doi: 10.1088/1674-1056/ace95b
    摘要 ( 186 )   HTML ( 1 )   PDF(1686KB) ( 79 )  
    Chromium atom photolithography gratings are a promising technology for the development of nanoscale length standard substances due to their high accuracy, uniformity, and consistency. However, the inherent difference between the interaction of positive and negative frequency detuning standing wave field and the atoms can cause a difference in the adjacent peak-to-valley heights of the grating in positive and negative frequency detuning chromium atom lithography, which greatly reduces its accuracy. In this study, we performed a controlled variable growth simulation using the semi-classical theoretical model and Monte Carlo method with trajectory tracking and ballistic deposition methods to investigate the influence of key experimental parameters on the surface growth process of positive and negative frequency detuning atomic lithography gratings. We established a theoretical model based on simulation results and summarized empirical equations to guide the selection of experimental parameters. Our simulations achieved uniform positive and negative frequency detuning atomic lithography gratings with a period of 1/4 of the wavelength corresponding to the atomic transition frequency, and adjacent peak-to-valley heights differing by no more than 2 nm, providing an important theoretical reference for the controllable fabrication of these gratings.
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    Quantum estimation of rotational speed in optomechanics
    Hao Li(李浩) and Jiong Cheng(程泂)
    2023 (10):  100602-100602.  doi: 10.1088/1674-1056/ace3b7
    摘要 ( 129 )   HTML ( 0 )   PDF(6305KB) ( 42 )  
    We study the quantum Fisher information (QFI) of the angular velocity of rotation in an optomechanical system. Based on the Gaussian measurements method, we derive the explicit form of a single-mode Gaussian QFI, which is valid for arbitrary angular velocity of rotation. The information about the angular velocity to be measured is contained in the optical covariance matrix, which can be experimentally determined via homodyne measurement. We find that QFI increases rapidly when driving the system close to the unstable boundary. This result can be attributed to the strong nonlinearity of the system at the unstable boundary. Our results indicate the possibility of using an optomechanical system for high precision detection of the angular velocity of rotation.
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    Disturbance observer-based fuzzy fault-tolerant control for high-speed trains with multiple disturbances
    Qian-Ling Wang(王千龄), Cai-Qing Ma(马彩青), and Xue Lin(林雪)
    2023 (10):  100701-100701.  doi: 10.1088/1674-1056/acdfbe
    摘要 ( 125 )   HTML ( 0 )   PDF(715KB) ( 25 )  
    The fault-tolerant control problem is investigated for high-speed trains with actuator faults and multiple disturbances. Based on the novel train model resulting from the Takagi-Sugeno fuzzy theory, a sliding-mode fault-tolerant control strategy is proposed. The norm bounded disturbances which are composed of interactive forces among adjacent carriages and basis running resistances are rearranged by the fuzzy linearity technique. The modeled disturbances described as an exogenous system are compensated for by a disturbance observer. Moreover, a sliding mode surface is constructed, which can transform the stabilization problem of position and velocity into the stabilization problem of position errors and velocity errors, i.e., the tracking problem of position and velocity. Based on the parallel distributed compensation method and the disturbance observer, the fault-tolerant controller is solved. The Lyapunov theory is used to prove the stability of the closed-loop system. The feasibility and effectiveness of the proposed fault-tolerant control strategy are illustrated by simulation results.
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    Quantum Stirling heat engine with squeezed thermal reservoir
    Nikolaos Papadatos
    2023 (10):  100702-100702.  doi: 10.1088/1674-1056/acc7f8
    摘要 ( 163 )   HTML ( 0 )   PDF(674KB) ( 73 )  
    We analyze the performance of a quantum Stirling heat engine (QSHE), using a two-level system and a harmonic oscillator as the working medium, that is in contact with a squeezed thermal reservoir and a cold reservoir. First, we derive closed-form expressions for the produced work and efficiency, which strongly depend on the squeezing parameter $r_{\rm h}$. Then, we prove that the effect of squeezing heats the working medium to a higher effective temperature, which leads to better overall performance. In particular, the efficiency increases with the degree of squeezing, surpassing the standard Carnot limit when the ratio of the temperatures of the hot and cold reservoirs is small. Furthermore, we derive the analytical expressions for the efficiency at maximum work and the maximum produced work in the high and low temperature regimes, and we find that at extreme temperatures the squeezing parameter $r_{\rm h}$ does not affect the performance of the QSHE. Finally, the performance of the QSHE depends on the nature of the working medium.
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    Lifetime measurement of the 3d9 2D3/2 metastable level in Mo15+ at an electron beam ion trap
    Jialin Liu(刘佳林), Yintao Wang(王银涛), Bingsheng Tu(屠秉晟), Liangyu Huang(黄良玉), Ran Si(司然), Jiguang Li(李冀光), Mingwu Zhang(张明武), Yunqing Fu(傅云清), Yaming Zou(邹亚明), and Ke Yao(姚科)
    2023 (10):  103201-103201.  doi: 10.1088/1674-1056/acf121
    摘要 ( 181 )   HTML ( 0 )   PDF(1052KB) ( 97 )  
    An experimental measurement of the lifetime of $3\rm d^9$ $^2{\rm D}_{3/2}$ metastable level in Mo$^{15+}$ is reported in this work. The Mo$^{15+}$ ions are produced and trapped in an electron beam ion trap with a magnetic field of 0.65 T. The decay photons emitted from $3\rm d^9$ $^2{\rm D}_{3/2}$ level are subsequently recorded via a cooled photomultiplier tube. Through meticulous scrutiny of potential systematic uncertainties affecting the measurement outcomes, we have determined the lifetime of Mo$^{15+}$ $3\rm d^9$ $^2{\rm D}_{3/2}$ metastable level to be 2.83(22) ms. The experimental result provides a clear distinguishment from existing calculations based on various theoretical approaches.
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    Electric field intensity measurement by using doublet electromagnetically induced transparency of cold Rb Rydberg atoms
    Ting Gong(宫廷), Shuai Shi(师帅), Zhonghua Ji(姬中华), Guqing Guo(郭古青), Xiaocong Sun(孙小聪), Yali Tian(田亚莉), Xuanbing Qiu(邱选兵), Chuanliang Li(李传亮), Yanting Zhao(赵延霆), and Suotang Jia(贾锁堂)
    2023 (10):  103202-103202.  doi: 10.1088/1674-1056/acf120
    摘要 ( 174 )   HTML ( 0 )   PDF(740KB) ( 151 )  
    We demonstrate a simple method to measure electric field intensity by using doublet electromagnetically induced transparency (EIT) spectra of cold Rb Rydberg atoms, where the frequency of the coupling laser does not need to be locked. Based on the Stark splitting of the Rb Rydberg state, 10D3/2, under electric fields and the corresponding calculated polarizabilities, the real electric field intensity is calculated using the difference in radio-frequency diffraction between two acousto-optic modulators, which acts as a frequency criterion that allows us to measure the electrical field without locking the coupling laser. The value measured by this simple method shows a good agreement with our previous work [Opt. Express 29 1558 (2021)] where the frequency of the coupling laser needs to be locked with an additional EIT spectrum based on atom vapor and a proportional-integral-differential feedback circuit. Our presented method can also be extended to the measurement of electric field based on hot Rydberg atom vapor, which has application in industry.
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    Effect of aggregation on thermally activated delayed fluorescence and ultralong organic phosphorescence: QM/MM study
    Qun Zhang(张群), Xiaofei Wang(王晓菲), Zhimin Wu(吴智敏), Xiaofang Li(李小芳), Kai Zhang(张凯), Yuzhi Song(宋玉志), Jianzhong Fan(范建忠), Chuan-Kui Wang(王传奎), and Lili Lin(蔺丽丽)
    2023 (10):  103301-103301.  doi: 10.1088/1674-1056/acb75d
    摘要 ( 164 )   HTML ( 0 )   PDF(5824KB) ( 22 )  
    Aggregation-induced thermally activated delayed fluorescence (TADF) phenomena have attracted extensive attention recently. In this paper, several theoretical models including monomer, dimer, and complex are used for the explanation of the luminescent properties of ($R$)-5-(9H-carbazol-9-yl)-2-(1,2,3,4-tetrahydronaphthalen-1-yl)isoindoline-1,3-dione (($R$)-ImNCz), which was recently reported [$Chemical Engineering Journal$ 418 129167 (2021)]. The polarizable continuum model (PCM) and the combined quantum mechanics and molecular mechanics (QM/MM) method are adopted in simulation of the property of the molecule in the gas phase, solvated in acetonitrile and in aggregation states. It is found that large spin--orbit coupling (SOC) constants and a smaller energy gap between the first singlet excited state and the first triplet excited state ($\Delta E_{\rm st}$) in prism-like single crystals (SC$_{\rm p}$-form) are responsible for the TADF of ($R$)-lmNCz, while no TADF is found in block-like single crystals (SC$_{\rm b}$-form) with a larger $\Delta E_{\rm st}$. The multiple ultralong phosphorescence (UOP) peaks in the spectrum are of complex origins, and they are related not only to ImNCz but also to a minor amount of impurities (ImNBd) in the crystal prepared in the laboratory. The dimer has similar phosphorescence emission wavelengths to the ($R$)-lmNCz-SC$_{\rm p}$ monomers. The complex composed of ($R$)-lmNCz and ($R$)-lmNBd contributes to the phosphorescent emission peak at about 600 nm, and the phosphorescent emission peak at about 650 nm is generated by ($R$)-lmNBd. This indicates that the impurity could also contribute to emission in molecular crystals. The present calculations clarify the relationship between the molecular aggregation and the light-emitting properties of the TADF emitters and will therefore be helpful for the design of potentially more useful TADF emitters.
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    Classic analogue of Autler-Townes-splitting transparency using a single magneto-optical ring resonator
    Liting Wu(吴利婷), Wenkang Cao(曹文康), and Haolin Jiang(蒋昊林)
    2023 (10):  104201-104201.  doi: 10.1088/1674-1056/acd9c1
    摘要 ( 121 )   HTML ( 1 )   PDF(6376KB) ( 42 )  
    We show that an optical transparency can be obtained by using only one single magneto-optical ring resonator. This effect is based on the splitting of counterclockwise and clockwise modes in the ring resonator. Within a proposed resonator-waveguide configuration the superposition between the two degeneracy broken modes produces a transparency window, which can be closed, open, and modified by tuning the applied magnetic field. This phenomenon is an analogue of Autler-Townes splitting, and the magnetic field is equivalent to the strong external pump field. We provide a theoretic analysis on the induced transparency, and numerically demonstrate the effect using full-wave simulation. Feasible implication of this effect and its potential applications are also discussed.
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    Active control of surface plasmon polaritons with phase change materials
    Yuan-Zhen Qi(漆元臻), Qiao Jiang(蒋瞧), Hong Xiang(向红), and De-Zhuan Han(韩德专)
    2023 (10):  104202-104202.  doi: 10.1088/1674-1056/accd5a
    摘要 ( 139 )   HTML ( 0 )   PDF(11145KB) ( 57 )  
    Active control of surface plasmon polaritons (SPPs) is highly desired for nanophotonics. Here we employ a phase change material Ge2Sb2Te5 (GST) to actively manipulate the propagating direction of SPPs at the telecom wavelength. By utilizing the phase transition-induced refractive index change of GST, coupled with interference effects, a nanoantenna pair containing GST is designed to realize switchable one-way launching of SPPs. Devices based on the nanoantenna pairs are proposed to manipulate SPPs, including the direction tuning of SPP beams, switchable SPP focusing, and switchable cosine-Gauss SPP beam generating. Our design can be employed in compact optical circuits and photonics integration.
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    Defogging computational ghost imaging via eliminating photon number fluctuation and a cycle generative adversarial network
    Yuge Li(李玉格) and Deyang Duan(段德洋)
    2023 (10):  104203-104203.  doi: 10.1088/1674-1056/acd8b2
    摘要 ( 162 )   HTML ( 0 )   PDF(750KB) ( 44 )  
    Imaging through fluctuating scattering media such as fog is of challenge since it seriously degrades the image quality. We investigate how the image quality of computational ghost imaging is reduced by fluctuating fog and how to obtain a high-quality defogging ghost image. We show theoretically and experimentally that the photon number fluctuations introduced by fluctuating fog is the reason for ghost image degradation. An algorithm is proposed to process the signals collected by the computational ghost imaging device to eliminate photon number fluctuations of different measurement events. Thus, a high-quality defogging ghost image is reconstructed even though fog is evenly distributed on the optical path. A nearly 100% defogging ghost image is obtained by further using a cycle generative adversarial network to process the reconstructed defogging image.
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    Quantum-enhanced optical precision measurement assisted by low-frequency squeezed vacuum states
    Guohui Kang(康国辉), Jinxia Feng(冯晋霞), Lin Cheng(程琳), Yuanji Li(李渊骥), and Kuanshou Zhang(张宽收)
    2023 (10):  104204-104204.  doi: 10.1088/1674-1056/acc520
    摘要 ( 169 )   HTML ( 0 )   PDF(824KB) ( 54 )  
    Stable low-frequency squeezed vacuum states at a wavelength of 1550 nm were generated. By controlling the squeezing angle of the squeezed vacuum states, two types of low-frequency quadrature-phase squeezed vacuum states and quadrature-amplitude squeezed vacuum states were obtained using one setup respectively. A quantum-enhanced fiber Mach-Zehnder interferometer (FMZI) was demonstrated for low-frequency phase measurement using the generated quadrature-phase squeezed vacuum states that were injected. When phase modulation was measured with the quantum-enhanced FMZI, there were above 3 dB quantum improvements beyond the shot-noise limit (SNL) from 40 kHz to 200 kHz, and 2.3 dB quantum improvement beyond the SNL at 20 kHz was obtained. The generated quadrature-amplitude squeezed vacuum state was applied to perform low-frequency amplitude modulation measurement for sensitivity beyond the SNL based on optical fiber construction. There were about 2 dB quantum improvements beyond the SNL from 60 kHz to 200 kHz. The current scheme proves that quantum-enhanced fiber-based sensors are feasible and have potential applications in high-precision measurements based on fiber, particularly in the low-frequency range.
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    Single-mode GaSb-based laterally coupled distributed-feedback laser for CO2 gas detection
    Shi-Xian Han(韩实现), Jin-Yi Yan(严进一), Chun-Fang Cao(曹春芳), Jin Yang(杨锦), An-Tian Du(杜安天), Yuan-Yu Chen(陈元宇), Ruo-Tao Liu(刘若涛), Hai-Long Wang(王海龙), and Qian Gong(龚谦)
    2023 (10):  104205-104205.  doi: 10.1088/1674-1056/accff2
    摘要 ( 153 )   HTML ( 0 )   PDF(1333KB) ( 29 )  
    We report on a GaSb-based laterally coupled distributed feedback (LC-DFB) laser with Cr gratings operating at 2004 nm for CO2 detection application. Butterfly packaged with single-mode fiber pigtailed, the laser diode operates in the continuous-wave mode in a temperature range from -10 ℃ to 60 ℃, with a maximum output power of 2 mW and a maximum side-mode suppression ratio over 30 dB. Wavelength-modulated absorption spectroscopy of CO2 demonstrates the applicability of the LC-DFB laser to tunable diode laser absorption spectroscopy. Furthermore, the diode junction temperature, which is measured by using the wavelength shift method, exhibits a maximum value of 17 ℃ in the single-mode operation range.
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    Milli-Joule pulses post-compressed from 14 ps to 475 fs in bulk-material multi-pass cell based on cylindrical vector beam
    Xu Zhang(张旭), Zhaohua Wang(王兆华), Xianzhi Wang(王羡之), Jiawen Li(李佳文), Jiajun Li(李佳俊), Guodong Zhao(赵国栋), and Zhiyi Wei(魏志义)
    2023 (10):  104206-104206.  doi: 10.1088/1674-1056/acd5c6
    摘要 ( 134 )   HTML ( 0 )   PDF(1214KB) ( 17 )  
    A cylindrical vector beam is utilized to enhance the energy scale of the pulse post-compressed in a bulk-material Herriott multi-pass cell (MPC). The method proposed here enables, for the first time to the best of our knowledge, pulse compression from 14 ps down to 475 fs with throughput energy beyond 1 mJ, corresponding to a compression ratio of 30, which is the highest pulse energy and compression ratio in single-stage bulk-material MPCs. Furthermore, we demonstrate the characteristic of the vector polarization beam is preserved in the MPC.
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    Adiabatic evolution of optical beams of arbitrary shapes in nonlocal nonlinear media
    Jiarui Che(车佳瑞), Yuxin Zheng(郑喻心), Guo Liang(梁果), and Qi Guo(郭旗)
    2023 (10):  104207-104207.  doi: 10.1088/1674-1056/acd689
    摘要 ( 148 )   HTML ( 0 )   PDF(1608KB) ( 43 )  
    We discuss evolution of Hermite-Gaussian beams of different orders in nonlocal nonlinear media whose characteristic length is set as different functions of propagation distance, using the variational approach. It is proved that as long as the characteristic length varies slowly enough, all the Hermite-Gaussian beams can propagate adiabatically. When the characteristic length gradually comes back to its initial value after changes, all the Hermite-Gaussian beams can adiabatically restore to their own original states. The variational results agree well with the numerical simulations. Arbitrary shaped beams synthesized by Hermite-Gaussian modes can realize adiabatic evolution in nonlocal nonlinear media with gradual characteristic length.
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    Theoretical analysis of the optical rotational Doppler effect under atmospheric turbulence by mode decomposition
    Sheng-Jie Ma(马圣杰), Shi-Long Xu(徐世龙), Xiao Dong(董骁), Xin-Yuan Zhang(张鑫源), You-Long Chen(陈友龙), and Yi-Hua Hu(胡以华)
    2023 (10):  104208-104208.  doi: 10.1088/1674-1056/acc1d0
    摘要 ( 168 )   HTML ( 0 )   PDF(1554KB) ( 69 )  
    The optical rotational Doppler effect associated with orbital angular momentum provides a new means for rotational velocity detection. In this paper, we investigate the influence of atmospheric turbulence on the rotational Doppler effect. First, we deduce the generalized formula of the rotational Doppler shift in atmospheric turbulence by mode decomposition. It is found that the rotational Doppler signal frequency spectrum will be broadened, and the bandwidth is related to the turbulence intensity. In addition, as the propagation distance increases, the bandwidth also increases. And when $C_{n}^{2} \le 5\times 10^{-15}$ m$^{-2/3}$ and $2z\le 2$ km, the rotational Doppler signal frequency spectrum width $d$ and the spiral spectrum width $d_{0}$ satisfy the relationship $d=2d_{0} -1$. Finally, we analyze the influence of mode crosstalk on the rotational Doppler effect, and the results show that it destroys the symmetrical distribution of the rotational Doppler spectrum about $2l\cdot \varOmega /2\pi$. This theoretical model enables us to better understand the generation of the rotational Doppler frequency and may help us better analyze the influence of the complex atmospheric environment on the rotational Doppler frequency.
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    Simultaneous detection of CH4 and CO2 through dual modulation off-axis integrated cavity output spectroscopy
    Yi-Xuan Liu(刘艺璇), Zhou-Bing Wang(王周兵), Xin-Xin Wei(韦欣欣), Jing-Jing Wang(王静静), Xin Meng(孟鑫), and Gui-Lin Mao(毛桂林)
    2023 (10):  104209-104209.  doi: 10.1088/1674-1056/acdac1
    摘要 ( 147 )   HTML ( 0 )   PDF(1027KB) ( 65 )  
    This study established a novel method for the simultaneous detection of two-component gases. Radio frequency (RF) white noise disturbance laser current and wavelength modulation were simultaneously used to improve the off-axis integrated cavity output spectroscopy technique, and a high-precision dual modulation OA-ICOS (RF-WM-OA-ICOS) system was established. The two laser beams were coupled into one laser beam that was applied incident to the cavity of RF-WM-OA-ICOS system. The second harmonic signals of CH$_{4}$ and CO$_{2}$ gas simultaneously appeared in the rising or falling edge of a triangular wave. This method was used to measure CH$_{4}$ and CO$_{2}$ with different concentrations. The results indicated that the proposed system has high stability and can accurately and simultaneously measure the concentrations of CH$_{4}$ and CO$_{2}$, with an optimal integration time of 220 s. The minimum detection limit was 10 ppb for CH$_{4}$ and 1.5 ppm for CO$_{2}$. The corresponding noise equivalent absorption sensitivity values were calculated as $2.67 \times 10^{-13}$ cm$^{-1}\cdot$Hz$^{-1/2}$ and $5.18 \times 10^{-11}$ cm$^{-1}\cdot$Hz$^{-1/2}$, respectively. The proposed dual-component gas simultaneous detection method can also be used for high-precision simultaneous detection of other gases. Therefore, this study may serve as a reference for developing portable multicomponent gas analyzers.
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    Design of a photonic crystal fiber polarization beam splitter with simple structure and ultra-wide bandwidth
    Yun-Peng Wei(魏云鹏), Jin-Hui Yuan(苑金辉), Yu-Wei Qu(屈玉玮), Shi Qiu(邱石), Xian Zhou(周娴), Bin-Bin Yan(颜玢玢), Kui-Ru Wang(王葵如), Xin-Zhu Sang(桑新柱), and Chong-Xiu Yu(余重秀)
    2023 (10):  104210-104210.  doi: 10.1088/1674-1056/accd54
    摘要 ( 160 )   HTML ( 0 )   PDF(944KB) ( 78 )  
    A novel polarization beam splitter (PBS) based on dual-core photonic crystal fiber (DC-PCF) is proposed in this work. The proposed DC-PCF PBS contains two kinds of lattices and three kinds of air holes to form the asymmetrical elliptic dual-core structure. By using the full-vector finite element method, the propagation characteristics of the proposed DC-PCF PBS are investigated. The simulation results show that the bandwidth of the proposed DC-PCF PBS can reach to 340 nm, which covers the S + C + L + U communication bands, the shortest splitting length is 1.97 mm, and the maximum extinction ratio appears near wavelength 1550 nm. Moreover, the insertion loss of the proposed DC-PCF PBS is very low. It is believed that the proposed DC-PCF PBS has important applications in the field of all-optical communication and network.
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    Atomic-scale electromagnetic theory bridging optics in microscopic world and macroscopic world
    Zhi-Yuan Li(李志远) and Jian-Feng Chen(陈剑锋)
    2023 (10):  104211-104211.  doi: 10.1088/1674-1056/acec41
    摘要 ( 188 )   HTML ( 2 )   PDF(796KB) ( 122 )  
    Atoms in the microscopic world are the basic building blocks of the macroscopic world. In this work, we construct an atomic-scale electromagnetic theory that bridges optics in the microscopic and macroscopic worlds. As the building block of the theory, we use the microscopic polarizability to describe the optical response of a single atom, solve the transport of electromagnetic wave through a single atomic layer under arbitrary incident angle and polarization of the light beam, construct the single atomic layer transfer matrix for light transport across the atomic layer. Based on this transfer matrix, we get the analytical form of the dispersion relation, refractive index, and transmission/reflection coefficient of the macroscopic medium. The developed theory can handle single-layer and few-layers of homogeneous and heterogeneous 2D materials, investigate homogeneous 2D materials with various vacancies or insertion atomic-layer defects, study compound 2D materials with a unit cell composed of several elements in both the lateral and parallel directions with respect to the light transport.
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    Efficient transfer of metallophosphor excitons via confined polaritons in organic nanocrystals
    Wenbin Lu(芦文斌), Yongcong Chen(陈永聪), Xuyun Yang(杨旭云), and Ping Ao(敖平)
    2023 (10):  104212-104212.  doi: 10.1088/1674-1056/acf03b
    摘要 ( 141 )   HTML ( 0 )   PDF(615KB) ( 140 )  
    We investigate the transfer of phosphorescent energy between co-assembled metallophosphors in crystalline nanostructures [Angew. Chem. Int. Ed. 57 7820 (2018) and J. Am. Chem. Soc. 140 4269 (2018)]. Neither Dexter's nor Förster's mechanism of resonance energy transfer (RET) could account fully for the observed rates, which exceed 85% with significant temperature dependence. But there exists an alternative pathway on RET mediated by intermediate states of resonantly confined exciton-polaritons. Such a mechanism was used to analyze artificial photosynthesis in organic fluorescents [Phys. Rev. Lett. 122 257402 (2019)]. For metallophosphors, the confined modes act as extended states lying between the molecular S1 and T1 states, offering a bridge for the long-lived T1 excitons to migrate from donors to acceptors. Population dynamics with parameters taken entirely based on experiments fits the observed lifetimes of phosphorescence across a broad range of doping and temperature.
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    Ground-state phase diagram, symmetries, excitation spectra and finite-frequency scaling of the two-mode quantum Rabi model
    Yue Chen(陈越), Maoxin Liu(刘卯鑫), and Xiaosong Chen(陈晓松)
    2023 (10):  104213-104213.  doi: 10.1088/1674-1056/acea66
    摘要 ( 134 )   HTML ( 1 )   PDF(650KB) ( 104 )  
    We investigate the two-mode quantum Rabi model (QRM) describing the interaction between a two-level atom and a two-mode cavity field. The quantum phase transitions are found when the ratio $ \eta $ of transition frequency of atom to frequency of cavity field approaches infinity. We apply the Schrieffer-Wolff (SW) transformation to derive the low-energy effective Hamiltonian of the two-mode QRM, thus yielding the critical point and rich phase diagram of quantum phase transitions. The phase diagram consists of four regions: a normal phase, an electric superradiant phase, a magnetic superradiant phase and an electromagnetic superradiant phase. The quantum phase transition between the normal phase and the electric (magnetic) superradiant phase is of second order and associates with the breaking of the discrete $ Z_2 $ symmetry. On the other hand, the phase transition between the electric superradiant phase and the magnetic superradiant phase is of first order and relates to the breaking of the continuous $U(1)$ symmetry. Several important physical quantities, for example the excitation energy and average photon number in the four phases, are derived. We find that the excitation spectra exhibit the Nambu-Goldstone mode. We calculate analytically the higher-order correction and finite-frequency exponents of relevant quantities. To confirm the validity of the low-energy effective Hamiltonians analytically derived by us, the finite-frequency scaling relation of the averaged photon numbers is calculated by numerically diagonalizing the two-mode quantum Rabi Hamiltonian.
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    State transfer and entanglement between two- and four-level atoms in a cavity
    Si-Wu Li(李思吾), Tianfeng Feng(冯田峰), Xiao-Long Hu(胡骁龙), and Xiaoqi Zhou(周晓祺)
    2023 (10):  104214-104214.  doi: 10.1088/1674-1056/acf205
    摘要 ( 200 )   HTML ( 0 )   PDF(1252KB) ( 128 )  
    Qudits with a large Hilbert space to host quantum information are widely utilized in various applications, such as quantum simulation and quantum computation, but the manipulation and scalability of qudits still face challenges. Here, we propose a scheme to directly and locally transfer quantum information from multiple atomic qubits to a single qudit and vice versa in an optical cavity. With the qubit-qudit interaction induced by the cavity, our scheme can transfer quantum states efficiently and measurement-independently. In addition, this scheme can robustly generate a high-dimensional maximal entangled state with asymmetric particle numbers, showing its potential in realizing an entanglement channel. Such an information interface for qubits and qudit may have enlightening significance for future research on quantum systems in hybrid dimensions.
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    Novel transmission property of zero-index metamaterial waveguide doped with gain and lossy defects
    Qionggan Zhu(朱琼干), Lichen Chai(柴立臣), and Hai Lu(路海)
    2023 (10):  104215-104215.  doi: 10.1088/1674-1056/acedf6
    摘要 ( 143 )   HTML ( 0 )   PDF(2251KB) ( 108 )  
    Taking inspiration from quantum parity-time (PT) symmetries that have gained immense popularity in the emerging fields of non- Hermitian optics and photonics, the interest of exploring more generalized gain-loss interactions is never seen down. In this paper we theoretically present new fantastic properties through a zero-index metamaterial (ZIM) waveguide loaded gain and loss defects. For the case of epsilon-and-mu-near-zero (EMNZ) based ZIM medium, electromagnetic (EM) waves are cumulative and the system behaves as an amplifier when the loss cavity coefficient is greater than the gain cavity coefficient. Conversely, when loss is less than gain, EM waves are dissipated and the system behaves as an attenuator. Moreover, our investigation is extended to non-Hermitian scenarios characterized by tailored distributions of gain and loss in the epsilon-near-zero (ENZ) host medium. The transport effect in ZIM waveguide is amplified in one mode, while it is dissipative in the other mode, which breaks the common sense and its physic is analyzed by magnetic flux. That is which cavity has the smaller loss/gain coefficient, the larger its magnetic flux, which cavity dominates. This paper is of significant importance in the manipulation of electromagnetic waves and light amplification as well as the enhancement of matter interactions.
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    Transmission effects of high energy nanosecond lasers in laser-induced air plasma under different pressures
    Wei-Min Hu(胡蔚敏), Kai-Xin Yin(尹凯欣), Xiao-Jun Wang(王小军), Jing Yang(杨晶), Ke Liu(刘可), Qin-Jun Peng(彭钦军), and Zu-Yan Xu(许祖彦)
    2023 (10):  105201-105201.  doi: 10.1088/1674-1056/acb0bf
    摘要 ( 170 )   HTML ( 0 )   PDF(815KB) ( 108 )  
    When a high energy nanosecond (ns) laser induces breakdown in the air, the plasma density generated in the rarefied atmosphere is much smaller than that at normal pressure. It is associated with a relatively lower absorption coefficient and reduces energy loss of the laser beam at low pressure. In this paper, the general transmission characterizations of a Joule level 10 ns 1064 nm focused laser beam are investigated both theoretically and experimentally under different pressures. The evolution of the electron density ($n_{\rm e}$), the changes in electron temperature ($T_{\rm e}$) and the variation of laser intensity ($I$) are employed for numerical analyses in the simulation model. For experiments, four optical image transfer systems with focal length ($f$) of 200 mm are placed in a chamber and employed to focus the laser beam and produce plasmas at the focus. The results suggest that the transmittance increases obviously with the decreasing pressure and the plasma channels on the transmission path can be observed by the self-illumination. The simulation results agree well with the experimental data. The numerical model presents that the maximum $n_{\rm e}$ at the focus can reach 10$^{19}$ cm$^{-3}$, which is far below the critical density ($n_{\rm c}$). As a result, the laser beam is not completely shielded by the plasmas.
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    Efficient ion acceleration driven by a Laguerre-Gaussian laser in near-critical-density plasma
    Jia-Xiang Gao(高嘉祥), Meng Liu(刘梦), and Wei-Min Wang(王伟民)
    2023 (10):  105202-105202.  doi: 10.1088/1674-1056/ace428
    摘要 ( 178 )   HTML ( 0 )   PDF(2923KB) ( 35 )  
    Laser-driven ion accelerators have the advantages of compact size, high density, and short bunch duration over conventional accelerators. Nevertheless, it is still challenging to generate ion beams with quasi-monoenergetic peak and low divergence in experiments with the current ultrahigh intensity laser and thin target technologies. Here we propose a scheme that a Laguerre-Gaussian laser irradiates a near-critical-density (NCD) plasma to generate a quasi-monoenergetic and low-divergence proton beam. The Laguerre-Gaussian laser pulse in an NCD plasma excites a moving longitudinal electrostatic field with a large amplitude, and it maintains the inward bowl-shape for dozens of laser durations. This special distribution of the longitudinal electrostatic field can simultaneously accelerate and converge the protons. Our particle-in-cell (PIC) simulation shows that the efficient proton acceleration can be realized with the Laguerre-Gaussian laser intensity ranging from $3.9\times {10}^{21}$ W$\cdot$cm$^{-2}$-$1.6\times 10^{22}$ W$\cdot$cm$^{-2}$ available in the near future, e.g., a quasi-monoenergetic proton beam with peak energy $\sim 115 $ MeV and divergence angles less than 5$^\circ$ can be generated by a $5.3\times 10^{21}$ W$\cdot $cm$^{-2}$ pulse. This work could provide a reference for the high-quality ion beam generation with PWclass laser systems available recently.
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    Effects of plasma radiation on the nonlinear evolution of neo-classical tearing modes in tokamak plasmas with reversed magnetic shear
    Shuai Jiang(姜帅), Zheng-Xiong Wang(王正汹), Lai Wei(魏来), and Tong Liu(刘桐)
    2023 (10):  105203-105203.  doi: 10.1088/1674-1056/acedf7
    摘要 ( 150 )   HTML ( 0 )   PDF(4572KB) ( 40 )  
    Effects of plasma radiation on the nonlinear evolution of neo-classical double tearing modes (NDTMs) in tokamak plasmas with reversed magnetic shear are numerically investigated based on a set of reduced magnetohydrodynamics (MHD) equations. Cases with different separations $\varDelta_{\rm rs} =\left| {r_{\rm s2} -r_{\rm s1} } \right|$ between the two same rational surfaces are considered. In the small $\varDelta_{\rm rs} $ cases, the plasma radiation destabilizes the NDTMs and makes the kinetic energy still grow gradually in the late nonlinear phase. Moreover, the NDTM harmonics with high mode numbers reach a high level in the presence of plasma radiation, forming a broad spectrum of MHD perturbations that induces a radially broadened region of MHD turbulence. As a result, the profiles of safety factors also enter a nonlinear oscillation phase. In the intermediate $\varDelta_{\rm rs} $ case, the plasma radiation can advance the explosive burst of kinetic energy that results from the fast driven reconnection between the two rational surfaces, because it can further promote the destabilizing effects of bootstrap current perturbation on the magnetic island near the outer rational surfaces. In the large $\varDelta_{\rm rs} $ case, through destabilizing the outer islands significantly, the plasma radiation can even induce the explosive burst in the reversed magnetic shear configuration where the burst cannot be induced in the absence of plasma radiation.
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    Ab initio study of chemical effect on structural properties of Ti-Al melts
    Yun Feng(冯运), Yan Feng(冯艳), and Hai-Long Peng(彭海龙)
    2023 (10):  106101-106101.  doi: 10.1088/1674-1056/acd2c0
    摘要 ( 110 )   HTML ( 1 )   PDF(642KB) ( 15 )  
    We study chemical effect on the structural properties of Ti-Al melts, with the Al concentration systematically changed, via ab initio molecular dynamics simulations. By calculating the partial coordination numbers, we find a preferred connection between the nearest neighbors for Al-Ti pairs. This induces an excess Ti coordination in the cluster characterized by local five-fold symmetry in Voronoi tessellation. Structural entropy measured from the diversity of Voronoi polyhedrons shows an intriguing non-monotonic tendency with concentration: it first decreases to a minimum value at $\mathrm{Ti}_{\mathrm{40}}\mathrm{Al}_{\mathrm{60}}$, and then increases beyond this concentration. This implies a more ordered local structure induced by the chemical interaction at the intermediate compositions. The spatial correlation among the crystalline-like or the icosahedral-like clusters also exhibits the highest intensity for Al-Ti pairs, verifying the important role played by the chemical interaction in the local structure connectivity.
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    Subtle lattice distortion-driven phase transitions in layered ACu4As2 (A = Eu, Sr)
    Yong Nie(聂勇), Zheng Chen(陈正), Ming Mei(梅明), Yuan-Yuan Wang(王园园), Jia-Ting Wu(吴嘉挺), Jia-Liang Jiang(蒋佳良), Wen-Hai Song(宋文海), Wei Ning(宁伟), Zhao-Sheng Wang(王钊胜), Xiang-De Zhu(朱相德), and Ming-Liang Tian(田明亮)
    2023 (10):  106102-106102.  doi: 10.1088/1674-1056/acd36b
    摘要 ( 167 )   HTML ( 0 )   PDF(1408KB) ( 38 )  
    The compounds composed of transition metal cations and pnictide anions provide a rich platform for studying novel physical phenomena. Here we report on the observation of a phase transition at $\sim 70$ K and 145 K in layered compound EuCu$_{4}$As$_{2}$ and SrCu$_{4}$As$_{2}$, respectively. from both the transport and heat capacity. The thermal expansion measurements show that the variation of the lattice parameters ($\Delta L_{b}/L_{ab}$) around $T_{\rm P}$ is much less than that for a typical crystalline phase transition. Our experimental results reveal that the transition in EuCu$_{4}$As$_{2}$ and SrCu$_{4}$As$_{2}$ should be driven by subtle structural-distortion.
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    Prediction of superionic state in LiH2 at conditions enroute to nuclear fusion
    Fude Li(李福德), Hao Wang(王豪), Jinlong Li(李津龙), and Huayun Geng(耿华运)
    2023 (10):  106103-106103.  doi: 10.1088/1674-1056/acea68
    摘要 ( 168 )   HTML ( 1 )   PDF(1059KB) ( 134 )  
    Hydrogen and lithium, along with their compounds, are crucial materials for nuclear fusion research. High-pressure studies have revealed intricate structural transitions in all these materials. However, research on lithium hydrides beyond LiH has mostly focused on the low-temperature regime. Here, we use density functional theory and ab initio molecular dynamics simulations to investigate the behavior of LiH2, a hydrogen-rich compound, near its melting point. Our study is particularly relevant to the low-pressure region of the compression pathway of lithium hydrides toward fusion. We discovered a premelting superionic phase transition in LiH2 that has significant implications for its mass transportation, elastic properties, and sound velocity. The theoretical boundary for the superionic transition and melting temperature was then determined. In contrast, we also found that the primary compound of lithium hydrides, LiH, does not exhibit a superionic transition. These findings have important implications for optimizing the compression path to achieve the ignition condition in inertial confinement fusion research, especially when lithium tritium-deuteride (LiTD) is used as the fuel.
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    Thermal stress damage mechanism in single-crystal germanium caused by 1080 nm laser irradiation
    Yin-Chuan Sha(沙银川), Ze-Wen Li(李泽文), Zhi-Chao Jia(贾志超), Bing Han(韩冰), and Xiao-Wu Ni(倪晓武)
    2023 (10):  106104-106104.  doi: 10.1088/1674-1056/acb41f
    摘要 ( 157 )   HTML ( 1 )   PDF(1229KB) ( 57 )  
    The process of thermal stress damage during 1080 nm laser ablation of single-crystal germanium was recorded in real time using a high-speed charge-coupled device. A three-dimensional finite element numerical model based on Fourier's heat conduction equation, Hooke's law and the Alexander-Hasson equation was developed to analyze the thermal stress damage mechanism involved. The damage morphology of the ablated samples was observed using an optical microscope. The results show that the cooling process has an important influence on fracture in the laser-irradiated region of single-crystal germanium. Fracture is the result of a combination of thermal stress and reduction in local yield strength.
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    Thermal Hall effect and the Wiedemann-Franz law in Chern insulator
    Anxin Wang(王安新) and Tao Qin(秦涛)
    2023 (10):  107301-107301.  doi: 10.1088/1674-1056/ace158
    摘要 ( 189 )   HTML ( 0 )   PDF(1961KB) ( 136 )  
    Thermal Hall effect, where a transverse temperature difference is generated by implementing a longitudinal temperature gradient and an external magnetic field in the perpendicular direction to systems, is a useful tool to reveal transport properties of quantum materials. A systematic study of the thermal Hall effect in a Chern insulator is still lacking. Here, using the Landauer-Büttiker formula, we investigated the thermal Hall transport of the Harper-Hofstadter model with flux $\varphi$=1/2 and its generalizations. We demonstrated that the Wiedemann-Franz law, which states that the thermal Hall conductivity is linearly proportional to the quantum Hall conductivity in the low temperature limit, is still valid in this Chern insulator, and that the thermal Hall conductivity can be used to characterize the topological properties of quantum materials.
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    Effects of strain on the flat band in twisted bilayer graphene
    Zhen Zhang(张镇), Lu Wen(文露), Youkai Qiao(乔友凯), and Zhiqiang Li(李志强)
    2023 (10):  107302-107302.  doi: 10.1088/1674-1056/acb2c1
    摘要 ( 169 )   HTML ( 0 )   PDF(4598KB) ( 76 )  
    Based on the effective continuum model, we systematically study the electronic band structures and density of states of twisted bilayer graphene near the magic angle under the influence of different types of strain, including shear strain, volume-preserving strain and biaxial strain. We find that the flat bands behave very differently under various types of strain. Volume-preserving strain generically leads to broader van Hove singularities associated with the flat bands compared with those under shear strain, with dissimilar strain direction dependence. The band structures and density of states under shear and volume-preserving strains change with the strain direction, while those under biaxial strain are independent of the direction of strain. In particular, the effect of biaxial strain on twisted bilayer graphene is geometrically and electronically similar to the influence of the twisted angle. Our results reveal the characteristic structures in the band structures and density of states under various types of strain, which can serve as fingerprints for exploring the effects of strain on the novel physics of this system.
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    Nonmonotonic anomalous Hall effect and anisotropic magnetoresistance in SrRuO3/PbZr0.52Ti0.48O3 heterostructures
    Zhen-Li Wang(王振礼), Chao-Yang Kang(康朝阳), Cai-Hong Jia(贾彩虹), Hai-Zhong Guo(郭海中), and Wei-Feng Zhang(张伟风)
    2023 (10):  107303-107303.  doi: 10.1088/1674-1056/accd58
    摘要 ( 169 )   HTML ( 0 )   PDF(2289KB) ( 96 )  
    We fabricate SrRuO3/PbZr0.52Ti0.48O3 heterostructures each with an in-plane tensile-strained SrRuO3 layer and investigate the effect of an applied electric field on anomalous Hall effect. The four-fold symmetry of anisotropic magnetoresistance and the nonmonotonic variation of anomalous Hall resistivity are observed. By applying positive electric field or negative electric field, the intersecting hump-like feature is suppressed or enhanced, respectively. The sign and magnitude of the anomalous Hall conductivity can be effectively controlled with an electric field under a high magnetic field. The electric-field-modulated anomalous Hall effect is associated with the magnetization rotation in SrRuO3. The experimental results are helpful in modulating the magnetization rotation in spintronic devices based on SrRuO3 heterostructures.
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    Strong anharmonicity-assisted low lattice thermal conductivities and high thermoelectric performance in double-anion Mo2AB2 (A = S, Se, Te; B=Cl, Br, I) semiconductors
    Haijun Liao(廖海俊), Le Huang(黄乐), Xing Xie(谢兴), Huafeng Dong(董华锋), Fugen Wu(吴福根), Zhipeng Sun(孙志鹏), and Jingbo Li(李京波)
    2023 (10):  107304-107304.  doi: 10.1088/1674-1056/ace314
    摘要 ( 180 )   HTML ( 0 )   PDF(5703KB) ( 97 )  
    The thermoelectric properties of layered Mo$_{2}AB_{2}$ ($A={\rm S}$, Se, Te; $B={\rm Cl}$, Br, I) materials are systematically investigated by first-principles approach. Soft transverse acoustic modes and direct Mo d-Mo d couplings give rise to strong anharmonicities and low lattice thermal conductivities. The double anions with distinctly different electronegativities of Mo$_{2}AB_{2}$ monolayers can reduce the correlation between electron transport and phonon scattering, and further benefit much to their good thermoelectric properties. Thermoelectric properties of these Mo$_{2}AB_{2}$ monolayers exhibit obvious anisotropies due to the direction-dependent chemical bondings and transport properties. Furthermore, their thermoelectric properties strongly depend on carrier type (n-type or p-type), carrier concentration and temperature. It is found that n-type Mo$_{2}AB_{2}$ monolayers can be excellent thermoelectric materials with high electric conductivity, $\sigma $, and figures of merit, $ZT$. Choosing the types of $A$ and $B$ anions of Mo$_{2}AB_{2}$ is an effective strategy to optimize their thermoelectric performance. These results provide rigorous understanding on thermoelectric properties of double-anions compounds and important guidance for achieving high thermoelectric performance in multi-anion compounds.
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    Optimization of thermoelectric properties in elemental tellurium via high pressure
    Dongyao Zhao(赵东尧), Manman Yang(杨曼曼), Hairui Sun(孙海瑞), Xin Chen(陈欣), Yongsheng Zhang(张永胜), and Xiaobing Liu(刘晓兵)
    2023 (10):  107305-107305.  doi: 10.1088/1674-1056/ace15e
    摘要 ( 187 )   HTML ( 1 )   PDF(9522KB) ( 143 )  
    High pressure and high temperature (HPHT) technology, as an extreme physical condition, plays an important role in regulating the properties of materials, having the advantages of enhancing doping efficiency, refining grain size, and manufacturing defects, therefore it is quite necessary to study the effectiveness on tuning thermoelectric properties. Elemental telluride, a potential candidate for thermoelectric materials, has the poor doping efficiency and high resistivity, which become an obstacle for practical applications. Here, we report the realization of a dual optimization of electrical behaviors and thermal conductivity through HPHT method combining with the introduction of black phosphorus. The results show the maximum $zT$ of 0.65 and an average $zT$ of 0.42 (300 K-610 K), which are increased by 55% and 68% in the synthesis pressure regulation system, respectively. This study clarifies that the HPHT method has significant advantages in modulating the thermoelectric parameters, providing a reference for seeking high performance thermoelectric materials.
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    Design and investigation of doping-less gate-all-around TFET with Mg2Si source material for low power and enhanced performance applications
    Pranav Agarwal, Sankalp Rai, Rakshit Y. A, and Varun Mishra
    2023 (10):  107310-107310.  doi: 10.1088/1674-1056/acd5c0
    摘要 ( 137 )   HTML ( 0 )   PDF(11989KB) ( 79 )  
    Metal-oxide-semiconductor field-effect transistor (MOSFET) faces the major problem of being unable to achieve a subthreshold swing (SS) below 60 mV/dec. As device dimensions continue to reduce and the demand for high switching ratios for low power consumption increases, the tunnel field-effect transistor (TFET) appears to be a viable device, displaying promising characteristic as an answer to the shortcomings of the traditional MOSFET. So far, TFET designing has been a task of sacrificing higher ON state current for low subthreshold swing (and $vice versa$), and a device that displays both while maintaining structural integrity and operational stability lies in the nascent stages of popular research. This work presents a comprehensive analysis of a heterojunction plasma doped gate-all-around TFET (HPD-GAA-TFET) by making a comparison between Mg$_{2}$Si and Si which serve as source materials. Charge plasma technique is employed to implement doping in an intrinsic silicon wafer with the help of suitable electrodes. A low-energy bandgap material, i.e. magnesium silicide is incorporated as source material to form a heterojunction between source and silicon-based channel. A rigorous comparison of performance between Si-based GAA-TFET and HPD-GAA-TFET is conducted in terms of electrical, radio frequency (RF), linearity, and distortion parameters. It is observable that HPD-GAA-TFET outperforms conventional Si-based GAA-TFET with an ON-state current ($I_{\rm ON}$), subthreshold swing (SS), threshold voltage ($V_{\rm th}$), and current switching ratio being 0.377 mA, 12.660 mV/dec, 0.214 V, and $2.985\times 10^{12}$, respectively. Moreover, HPD-GAA-TFET holds faster switching and is more reliable than Si-based device. Therefore, HPD-GAA-TFET is suitable for low-power applications.
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    First-principles study of moderate phonon-mediated pairing in high-pressure monoclinic phase of BiS2-based superconductors
    Jie Cheng(程杰), Yu-Lan Cheng(程玉兰), Bin Li(李斌), and Sheng-Li Liu(刘胜利)
    2023 (10):  107401-107401.  doi: 10.1088/1674-1056/accd56
    摘要 ( 146 )   HTML ( 0 )   PDF(971KB) ( 25 )  
    Isotope effect on superconductive transition temperature ($T_{\rm c}$) is an essential indicator to examine whether the mechanism of superconductors is conventional. Unconventional isotope effect of BiS$_{2}$-based superconductors has been previously reported in ambient-pressure tetragonal phase. However, to comprehensively ascertain the nature of superconductivity, the investigation of BiS$_{2}$-based system in high-pressure structure is highly desirable. In this work, we carried out the first-principles calculations of phonon spectra and superconductivity in high-pressure monoclinic phase of LaO$_{0.5}$F$_{0.5}$BiS$_{2}$ with $^{32}$S and $^{34}$S, and observed that the corresponding isotope coefficient is $0.13 \le \alpha\le 0.20$. This value is much greater than that of BiS$_{2}$-based superconductors in ambient-pressure phase, but slightly smaller than that of conventional MgB$_{2}$. Taking into account the calculated $T_{\rm c}$ lower than experimental results, we finally conclude that the moderate phonon-mediated pairing plays a significant role in forming superconductivity of BiS$_{2}$-based system in high-pressure phase, moreover, the cooperative multiple paring interactions should also be considered.
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    Enhanced ferromagnetism and conductivity of ultrathin freestanding La0.7Sr0.3MnO3 membranes
    Siqi Shan(单思齐), Yequan Chen(陈业全), Yongda Chen(陈勇达), Wenzhuo Zhuang(庄文卓), Ruxin Liu(刘汝新), Xu Zhang(张旭), Rong Zhang(张荣), and Xuefeng Wang(王学锋)
    2023 (10):  107402-107402.  doi: 10.1088/1674-1056/ace161
    摘要 ( 144 )   HTML ( 1 )   PDF(1015KB) ( 105 )  
    We report a universal method to transfer freestanding La0.7Sr0.3MnO3 membranes to target substrates. The 4-unit-cell-thick freestanding La0.7Sr0.3MnO3 membrane exhibits the enhanced ferromagnetism, conductivity and out-of-plane magnetic anisotropy, which otherwise shows nonmagnetic/antiferromagnetic and insulating behavior due to the intrinsic epitaxial strain. This work facilitates the promising applications of ultrathin freestanding correlated oxide membranes in electronics and spintronics.
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    Asymmetric scattering behaviors of spin wave dependent on magnetic vortex chirality
    Xue-Feng Zhang(张雪枫), Je-Ho Shim(沈帝虎), Xiao-Ping Ma(马晓萍), Cheng Song(宋成), Haiming Yu(于海明), and Hong-Guang Piao(朴红光)
    2023 (10):  107501-107501.  doi: 10.1088/1674-1056/acd36a
    摘要 ( 144 )   HTML ( 0 )   PDF(1476KB) ( 52 )  
    We investigate asymmetric spin wave scattering behaviors caused by vortex chirality in a cross-shaped ferromagnetic system by using the micromagnetic simulations. In the system, four scattering behaviors are found: (i) asymmetric skew scattering, depending on the polarity of vortex core, (ii) back scattering (reflection), depending on the vortex core stiffness, (iii) side deflection scattering, depending on structural symmetry of the vortex circulation, and (iv) geometrical scattering, depending on waveguide structure. The first and second scattering behaviors are attributed to nonlinear topological magnon spin Hall effect related to magnon spin-transfer torque effect, which has value for magnonic exploration and application.
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    Anomalous Hall effect in ferromagnetic LaCo2As2 and ferrimagnetic NdCo2As2
    Yu-Qing Huang(黄雨晴), Peng-Yu Zheng(郑鹏宇), Rui Liu(刘瑞), Xi-Tong Xu(许锡童), Zi-Yang Wu(吴紫阳), Chao Dong(董超), Jun-Feng Wang(王俊峰), Zhi-Ping Yin(殷志平), and Shuang Jia(贾爽)
    2023 (10):  107502-107502.  doi: 10.1088/1674-1056/acd925
    摘要 ( 141 )   HTML ( 0 )   PDF(1583KB) ( 89 )  
    We conducted a comparative study of the magnetic and transport properties of single-crystalline LaCo2As2 and NdCo2As2. LaCo2As2 is a soft metallic ferromagnet which exhibits purely intrinsic anomalous Hall effect (AHE) due to Co-3d electrons. With Nd-4f electronic magnetism, ferrimagnetic NdCo2As2 manifests pronounced sign reversal and multiple hysteresis loops in temperature- and field-dependent magnetization, Hall resistivity, and magnetoresistance, due to complicated magnetic structural changes. We reveal that the AHE for NdCo2As2 is stemming from the Co sub-lattice and deduce its phase diagram which includes magnetic compensation and two meta-magnetic phase transitions. The sensitivity of the Hall effect on the details of the magnetic structures in ferrimagnetic NdCo2As2 provides a unique opportunity to explore the magnetic interaction between 4f and 3d electrons and its impact on the electronic structure.
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    Optimization of the grain boundary diffusion process by doping gallium and zirconium in Nd-Fe-B sintered magnets
    Zhiteng Li(李之藤), Haibo Xu(徐海波), Feng Liu(刘峰), Rongshun Lai(赖荣舜), Renjie Wu(武仁杰), Zhibin Li(李志彬), Yangyang Zhang(张洋洋), and Qiang Ma(马强)
    2023 (10):  107503-107503.  doi: 10.1088/1674-1056/acd61f
    摘要 ( 183 )   HTML ( 0 )   PDF(1659KB) ( 118 )  
    As the channel for grain boundary diffusion (GBD) in Nd-Fe-B magnets, grain boundary (GB) phases have a very important effect on GBD. As doping elements that are commonly used to regulate the GB phases in Nd-Fe-B sintered magnets, the influences of Ga and Zr on GBD were investigated in this work. The results show that the Zr-doped magnet has the highest coercivity increment (7.97 kOe) by GBD, which is almost twice that of the Ga-doped magnet (4.32 kOe) and the magnet without Ga and Zr (3.24 kOe). Microstructure analysis shows that ZrB2 formed in the Zr-doped magnet plays a key role in increasing the diffusion depth. A continuous diffusion channel in the magnet can form because of the presence of ZrB2. ZrB2 can also increase the defect concentration in GB phases, which can facilitate GBD. Although Ga can also improve the diffusion depth, its effect is not very obvious. The micromagnetic simulation based on the experimental results also proves that the distribution of Tb in the Zr-doped magnet after GBD is beneficial to coercivity. This study reveals that the doping elements Ga and Zr in Nd-Fe-B play an important role in GBD, and could provide a new perspective for researchers to improve the effects of GBD.
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    Spin torque oscillator based on magnetic tunnel junction with MgO cap layer for radio-frequency-oriented neuromorphic computing
    Huayao Tu(涂华垚), Yanxiang Luo(雒雁翔), Kexin Zeng(曾柯心), Yuxuan Wu(吴宇轩), Like Zhang(张黎可), Baoshun Zhang(张宝顺), and Zhongming Zeng(曾中明)
    2023 (10):  107504-107504.  doi: 10.1088/1674-1056/acb424
    摘要 ( 160 )   HTML ( 2 )   PDF(976KB) ( 69 )  
    Recently, it has been proposed that spin torque oscillators (STOs) and spin torque diodes could be used as artificial neurons and synapses to directly process microwave signals, which could lower latency and power consumption greatly. However, one critical challenge is to make the microwave emission frequency of the STO stay constant with a varying input current. In this work, we study the microwave emission characteristics of STOs based on magnetic tunnel junction with MgO cap layer. By applying a small magnetic field, we realize the invariability of the microwave emission frequency of the STO, making it qualified to act as artificial neuron. Furthermore, we have simulated an artificial neural network using STO neuron to recognize the handwritten digits in the Mixed National Institute of Standards and Technology database, and obtained a high accuracy of 92.28%. Our work paves the way for the development of radio-frequency-oriented neuromorphic computing systems.
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    Eigenstates and temporal dynamics in cavity optomagnonics
    Yun-Jing Ding(丁云静) and Yang Xiao(肖杨)
    2023 (10):  107601-107601.  doi: 10.1088/1674-1056/acf039
    摘要 ( 171 )   HTML ( 0 )   PDF(511KB) ( 157 )  
    Many studies of magnon-photon coupling are performed in the frequency domain for microwave photons. In this work, we present analytical results of eigenfrequency, eigenstates, and temporal dynamics for the coupling between ferromagnetic magnon and visible photon. In contrast to microwave photons, optical photons can be coupled with magnon in a dispersive interaction which produces both level repulsion and attraction by varying the magnon-photon frequency detuning. At resonance, the hybridized states are of linear polarization and circular polarization for level repulsion and level attraction respectively. As the detuning increases, the polarizations of level repulsion remain linear but those of level attraction vary from elliptical to linear polarizations. The temporal dynamics of level repulsion presents the beat-like behavior. The level attraction presents monotonous decay in the weak coupling regime but gives rise to instability in the strong coupling regime due to the magnon amplification. As the detuning is large, both magnon and photon amplitudes present a synchronizing oscillation. Our results are important for exploring the temporal evolution of magnon-photon coupling in the range of optical frequency and designing magnon-based timing devices.
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    Improving efficiency of n-i-p perovskite solar cells enabled by 3-carboxyphenylboronic acid additive
    Bin-Jie Li(李斌杰), Jia-Wen Li(李嘉文), Gen-Jie Yang(杨根杰), Meng-Ge Wu(吴梦鸽), and Jun-Sheng Yu(于军胜)
    2023 (10):  107801-107801.  doi: 10.1088/1674-1056/ace1d8
    摘要 ( 151 )   HTML ( 1 )   PDF(1557KB) ( 111 )  
    In the past period of time, perovskite solar cells have gained tremendous developments in improving photovoltaic performance, but they still face severe challenges. Defects in perovskite layers, especially at grain boundaries, severely limit the stabilization and efficiency of solar cells. In this work, we adopt 3-carboxyphenylboronic acid (CPBA) for modifying defects in perovskite thin films. Through the interaction among the carboxyl group, boronic acid and lead ions in the perovskite film, the crystallization effect of the perovskite molecular is greatly optimized. Moreover, the film defects are spontaneously passivated and the band gap is reduced, increasing the open circuit voltage and fill factor. Therefore, power conversion efficiency has been increased from 17.25% to 20.20%. This discovery provides a potential strategy for passivating the trap states in perovskite and enhancing the properties of devices.
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    Photonic Dirac cone and topological transition in a moving dielectric slab
    Xinyang Pan(潘昕阳), Haitao Li(李海涛), Weijie Dong(董为杰), Xiaoxi Zhou(周萧溪), Gang Wang(王钢), and Bo Hou(侯波)
    2023 (10):  107802-107802.  doi: 10.1088/1674-1056/ace1d7
    摘要 ( 163 )   HTML ( 0 )   PDF(5083KB) ( 239 )  
    The moving media theory is applied to a photonic confined structure which is a continuous dielectric slab waveguide with the uniaxial anisotropy and without the discrete translational symmetry. The moving effect not only brings about non-reciprocity to the whole photonic band structure in the co-moving and counter-moving directions, but also leads to the topological transition of local degenerate points within the band diagram. We demonstrate through calculation that the type-II Dirac point can be turned into type-I Dirac point when the uniaxial slab is moving over certain speed. Our results provide a new approach to regulate the topology of degeneracy for two-dimensional photonic bands in the continuous translational symmetry condition.
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    Novel GaN-based double-channel p-heterostructure field-effect transistors with a p-GaN insertion layer
    Xuerui Niu(牛雪锐), Bin Hou(侯斌), Meng Zhang(张濛), Ling Yang(杨凌), Mei Wu(武玫), Xinchuang Zhang(张新创), Fuchun Jia(贾富春), Chong Wang(王冲), Xiaohua Ma(马晓华), and Yue Hao(郝跃)
    2023 (10):  108101-108101.  doi: 10.1088/1674-1056/acc7f4
    摘要 ( 173 )   HTML ( 0 )   PDF(720KB) ( 150 )  
    GaN-based p-channel heterostructure field-effect transistors (p-HFETs) face significant constraints on on-state currents compared with n-channel high electron mobility transistors. In this work, we propose a novel double heterostructure which introduces an additional p-GaN insertion layer into traditional p-HFETs. The impact of the device structure on the hole densities and valence band energies of both the upper and lower channels is analyzed by using Silvaco TACD simulations, including the thickness of the upper AlGaN layer and the doping impurities and concentration in the GaN buffer layer, as well as the thickness and Mg-doping concentration in the p-GaN insertion layer. With the help of the p-GaN insertion layer, the C-doping concentration in the GaN buffer layer can be reduced, while the density of the two-dimensional hole gas in the lower channel is enhanced at the same time. This work suggests that a double heterostructure with a p-GaN insertion layer is a better approach to improve p-HFETs compared with those devices with C-doped buffer layer alone.
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    Ferroelectricity of pristine Hf0.5Zr0.5O2 films fabricated by atomic layer deposition
    Luqiu Chen(陈璐秋), Xiaoxu Zhang(张晓旭), Guangdi Feng(冯光迪), Yifei Liu(刘逸飞), Shenglan Hao(郝胜兰), Qiuxiang Zhu(朱秋香), Xiaoyu Feng(冯晓钰), Ke Qu(屈可), Zhenzhong Yang(杨振中), Yuanshen Qi(祁原深), Yachin Ivry, Brahim Dkhil, Bobo Tian(田博博), Junhao Chu(褚君浩), and Chungang Duan(段纯刚)
    2023 (10):  108102-108102.  doi: 10.1088/1674-1056/accff3
    摘要 ( 164 )   HTML ( 0 )   PDF(1438KB) ( 124 )  
    Hafnium-based ferroelectric films, remaining their ferroelectricity down to nanoscale thickness, present a promising application for low-power logic devices and nonvolatile memories. It has been appealing for researchers to reduce the required temperature to obtain the ferroelectric phase in hafnium-based ferroelectric films for applications such as flexible and wearable electronics. This work demonstrates that a remanent polarization ($P_{\rm r}$) value of $> 5 $ μC/cm$^{2}$ can be obtained in as-deposited Hf$_{0.5}$Zr$_{0.5}$O$_{2}$ (HZO) films that are fabricated by thermal atomic layer deposition (TALD) under low temperature of 250 ℃. The ferroelectric orthorhombic phase (o-phase) in the as-deposited HZO films is detected by scanning transmission electron microscopy (STEM). This low fabrication temperature further extends the compatibility of ferroelectric HZO films to flexible electronics and avoids the cost imposed by following high-temperature annealing treatments.
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    Influence of carbon sources on the performance of carbon-coated nano-silicon
    Lin Wang(王琳), Na Li(李娜), Hao-Sen Chen(陈浩森), and Wei-Li Song(宋维力)
    2023 (10):  108201-108201.  doi: 10.1088/1674-1056/acb9e9
    摘要 ( 160 )   HTML ( 0 )   PDF(2529KB) ( 27 )  
    Silicon-based material is an important anode material for next-generation lithium-ion batteries. In order to overcome its shortcomings, carbon coating is often employed to improve the electrochemical performance. However, the carbon source, carbon content, and different contact and mixing schemes between carbon sources and silicon are all complex factors and need to be clarified. In this study, nano-silicon is coated by the chemical vapor deposition method using different carbon sources, such as acetylene, methane, propane, and propylene. Carbon content after coating is designed to stay at the same level to reduce the experimental error. Results show the sample with higher conductivity provides higher cycle performance. Propylene is the best choice of the four carbon sources studied in this work. These results indicate that the selection of the carbon source is an important factor that plays a significant role in electrochemical performance.
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    Improvement of energy resolution of x-ray transition-edge sensor using K-means algorithm and Wiener filter
    Qingxiao Ma(马卿效), Wen Zhang(张文), Peizhan Li(李佩展), Zheng Wang(王争), Zhifa Feng(冯志发), Xinkai Yang(杨心开), Jiaqiang Zhong(钟家强), Wei Miao(缪巍), Yuan Ren(任远), Jing Li(李婧), and Shengcai Shi(史生才)
    2023 (10):  108501-108501.  doi: 10.1088/1674-1056/acd7d4
    摘要 ( 138 )   HTML ( 0 )   PDF(983KB) ( 47 )  
    We develop an x-ray Ti/Au transition-edge sensor (TES) with an Au absorber deposited on the center of TES and improved its energy resolution using the K-means clustering algorithm in combination with Wiener filter. We firstly extract the main parameters of each recorded pulse trace, which are adopted to classify these traces into several clusters in the K-means clustering algorithm. Then real traces are selected for energy resolution analysis. Following the baseline correction, the Wiener filter is used to improve the signal-to-noise ratio. Although the silicon underneath the TES has not been etched to reduce the thermal conductance, the energy resolution of the developed x-ray TES is improved from 94 eV to 44 eV at 5.9 keV.
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    Ambipolar performance improvement of the C-shaped pocket TFET with dual metal gate and gate-drain underlap
    Zi-Miao Zhao(赵梓淼), Zi-Xin Chen(陈子馨), Wei-Jing Liu(刘伟景), Nai-Yun Tang(汤乃云), Jiang-Nan Liu(刘江南), Xian-Ting Liu(刘先婷), Xuan-Lin Li(李宣霖), Xin-Fu Pan(潘信甫), Min Tang(唐敏), Qing-Hua Li(李清华), Wei Bai(白伟), and Xiao-Dong Tang(唐晓东)
    2023 (10):  108502-108502.  doi: 10.1088/1674-1056/acbaf3
    摘要 ( 131 )   HTML ( 0 )   PDF(1029KB) ( 27 )  
    Dual-metal gate and gate-drain underlap designs are introduced to reduce the ambipolar current of the device based on the C-shaped pocket TFET(CSP-TFET). The effects of gate work function and gate-drain underlap length on the DC characteristics and analog/RF performance of CSP-TFET devices, such as the on-state current ($I_{\rm on}$), ambipolar current ($I_{\rm amb}$), transconductance ($g_{\rm m}$), cut-off frequency ($f_{\rm T}$) and gain-bandwidth product (GBP), are analyzed and compared in this work. Also, a combination of both the dual-metal gate and gate-drain underlap designs has been proposed for the C-shaped pocket dual metal underlap TFET (CSP-DMUN-TFET), which contains a C-shaped pocket area that significantly increases the on-state current of the device; this combination design substantially reduces the ambipolar current. The results show that the CSP-DMUN-TFET demonstrates an excellent performance, including high $I_{\rm on}$ ($9.03\times 10^{-4}$ A/μm), high $I_{\rm on}/I_{\rm off}$ ($\sim 10^{11}$), low SS$_{\rm avg}$ ($\sim 13 $ mV/dec), and low $I_{\rm amb}$ ($2.15\times 10^{-17}$ A/μm). The CSP-DMUN-TFET has the capability to fully suppress ambipolar currents while maintaining high on-state currents, making it a potential replacement in the next generation of semiconductor devices.
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    Proton induced radiation effect of SiC MOSFET under different bias
    Hong Zhang(张鸿), Hong-Xia Guo(郭红霞), Zhi-Feng Lei(雷志锋), Chao Peng(彭超), Wu-Ying Ma(马武英), Di Wang(王迪), Chang-Hao Sun(孙常皓), Feng-Qi Zhang(张凤祁), Zhan-Gang Zhang(张战刚), Ye Yang(杨业), Wei Lv(吕伟), Zhong-Ming Wang(王忠明), Xiang-Li Zhong(钟向丽), and Xiao-Ping Ouyang(欧阳晓平)
    2023 (10):  108503-108503.  doi: 10.1088/1674-1056/acbe31
    摘要 ( 151 )   HTML ( 0 )   PDF(1463KB) ( 117 )  
    Radiation effects of silicon carbide metal-oxide-semiconductor field-effect transistors (SiC MOSFETs) induced by 20 MeV proton under drain bias ($V_{\rm D}=800 $ V, $V_{\rm G}=0 $ V), gate bias ($V_{\rm D}=0 $ V, $V_{\rm G}=10$ V), turn-on bias ($V_{\rm D}=0.5 $ V, $V_{\rm G}=4 $ V) and static bias ($V_{\rm D}=0$ V, $V_{\rm G}=0 $ V) are investigated. The drain current of SiC MOSFET under turn-on bias increases linearly with the increase of proton fluence during the proton irradiation. When the cumulative proton fluence reaches $2 \times 10^{11}$ p$\cdot $cm$^{-2}$, the threshold voltage of SiC MOSFETs with four bias conditions shifts to the left, and the degradation of electrical characteristics of SiC MOSFETs with gate bias is the most serious. In the deep level transient spectrum test, it is found that the defect energy level of SiC MOSFET is mainly the ON2 ($E_{\rm c}-1.1$ eV) defect center, and the defect concentration and defect capture cross section of SiC MOSFET with proton radiation under gate bias increase most. By comparing the degradation of SiC MOSFET under proton cumulative irradiation, equivalent 1 MeV neutron irradiation and gamma irradiation, and combining with the defect change of SiC MOSFET under gamma irradiation and the non-ionizing energy loss induced by equivalent 1 MeV neutron in SiC MOSFET, the degradation of SiC MOSFET induced by proton is mainly caused by ionizing radiation damage. The results of TCAD analysis show that the ionizing radiation damage of SiC MOSFET is affected by the intensity and direction of the electric field in the oxide layer and epitaxial layer.
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    Investigation of Ga2O3/diamond heterostructure solar-blind avalanche photodiode via TCAD simulation
    Dun-Zhou Xu(许敦洲), Peng Jin(金鹏), Peng-Fei Xu(徐鹏飞), Meng-Yang Feng(冯梦阳), Ju Wu(吴巨), and Zhan-Guo Wang(王占国)
    2023 (10):  108504-108504.  doi: 10.1088/1674-1056/acc44d
    摘要 ( 168 )   HTML ( 3 )   PDF(881KB) ( 211 )  
    A Ga2O3/diamond separate absorption and multiplication avalanche photodiode (SAM-APD) with mesa structure has been proposed and simulated. The simulation is based on an optimized Ga2O3/diamond heterostructure TCAD physical model, which is revised by repeated comparison with the experimental data from the literature. Since both Ga2O3 and diamond are ultra-wide bandgap semiconductor materials, the Ga2O3/diamond SAM-APD shows good solar-blind detection ability, and the corresponding cutoff wavelength is about 263 nm. The doping distribution and the electric field distribution of the SAM-APD are discussed, and the simulation results show that the gain of the designed device can reach 5×104 and the peak responsivity can reach a value as high as 78 A/W.
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    Multilevel optoelectronic hybrid memory based on N-doped Ge2Sb2Te5 film with low resistance drift and ultrafast speed
    Ben Wu(吴奔), Tao Wei(魏涛), Jing Hu(胡敬), Ruirui Wang(王瑞瑞), Qianqian Liu(刘倩倩), Miao Cheng(程淼), Wanfei Li(李宛飞), Yun Ling(凌云), and Bo Liu(刘波)
    2023 (10):  108505-108505.  doi: 10.1088/1674-1056/ace765
    摘要 ( 170 )   HTML ( 0 )   PDF(5624KB) ( 124 )  
    Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed, scalable and non-volatile characteristics. However, the contradiction between thermal stability and operation speed is one of key factors to restrain the development of phase-change memory. Here, N-doped Ge2Sb2Te5-based optoelectronic hybrid memory is proposed to simultaneously implement high thermal stability and ultrafast operation speed. The picosecond laser is adopted to write/erase information based on reversible phase transition characteristics whereas the resistance is detected to perform information readout. Results show that when N content is 27.4 at.%, N-doped Ge2Sb2Te5 film possesses high ten-year data retention temperature of 175 ℃ and low resistance drift coefficient of 0.00024 at 85 ℃, 0.00170 at 120 ℃, and 0.00249 at 150 ℃, respectively, owing to the formation of Ge-N, Sb-N, and Te-N bonds. The SET/RESET operation speeds of the film reach 520 ps/13 ps. In parallel, the reversible switching cycle of the corresponding device is realized with the resistance ratio of three orders of magnitude. Four-level reversible resistance states induced by various crystallization degrees are also obtained together with low resistance drift coefficients. Therefore, the N-doped Ge2Sb2Te5 thin film is a promising phase-change material for ultrafast multilevel optoelectronic hybrid storage.
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    An accurate analytical surface potential model of heterojunction tunnel FET
    Yunhe Guan(关云鹤), Huan Li(黎欢), Haifeng Chen(陈海峰), and Siwei Huang(黄思伟)
    2023 (10):  108506-108506.  doi: 10.1088/1674-1056/accd48
    摘要 ( 124 )   HTML ( 0 )   PDF(1646KB) ( 54 )  
    Based on the accurate and efficient thermal injection method, we develop a fully analytical surface potential model for the heterojunction tunnel field-effect transistor (H-TFET). This model accounts for both the effects of source depletion and inversion charge, which are the key factors influencing the charge, capacitance and current in H-TFET. The accuracy of the model is validated against TCAD simulation and is greatly improved in comparison with the conventional model based on Maxwell-Boltzmann approximation. Furthermore, the dependences of the surface potential and electric field on biases are well predicted and thoroughly analyzed.
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    Kinesin-microtubule interaction reveals the mechanism of kinesin-1 for discriminating the binding site on microtubule
    Yi-Zhao Geng(耿轶钊), Li-Ai Lu(鲁丽爱), Ning Jia(贾宁), Bing-Bing Zhang(张冰冰), and Qing Ji(纪青)
    2023 (10):  108701-108701.  doi: 10.1088/1674-1056/acdfc1
    摘要 ( 163 )   HTML ( 0 )   PDF(1561KB) ( 40 )  
    Microtubule catalyzes the mechanochemical cycle of kinesin, a kind of molecular motor, through its crucial roles in kinesin's gating, ATPase and force-generation process. These functions of microtubule are realized through the kinesin-microtubule interaction. The binding site of kinesin on the microtubule surface is fixed. For most of the kinesin-family members, the binding site on microtubule is in the groove between $\alpha $-tubulin and $\beta $-tubulin in a protofilament. The mechanism of kinesin searching for the appropriate binding site on microtubule is still unclear. Using the molecular dynamics simulation method, we investigate the interactions between kinesin-1 and the different binding positions on microtubule. The key non-bonded interactions between the motor domain and tubulins in kinesin's different nucleotide-binding states are listed. The differences of the amino-acid sequences between $\alpha$- and $\beta$-tubulins make kinesin-1 binding to the $\alpha$-$\beta$ groove much more favorable than to the $\beta$-$\alpha$ groove. From these results, a two-step mechanism of kinesin-1 to discriminate the correct binding site on microtubule is proposed. Most of the kinesin-family members have the conserved motor domain and bind to the same site on microtubule, the mechanism may also be shared by other family members of kinesin.
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    Combination of density-clustering and supervised classification for event identification in single-molecule force spectroscopy data
    Yongyi Yuan(袁泳怡), Jialun Liang(梁嘉伦), Chuang Tan(谭创), Xueying Yang(杨雪滢), Dongni Yang(杨东尼), and Jie Ma(马杰)
    2023 (10):  108702-108702.  doi: 10.1088/1674-1056/acf03e
    摘要 ( 471 )   HTML ( 6 )   PDF(2308KB) ( 510 )  
    Single-molecule force spectroscopy (SMFS) measurements of the dynamics of biomolecules typically require identifying massive events and states from large data sets, such as extracting rupture forces from force-extension curves (FECs) in pulling experiments and identifying states from extension-time trajectories (ETTs) in force-clamp experiments. The former is often accomplished manually and hence is time-consuming and laborious while the latter is always impeded by the presence of baseline drift. In this study, we attempt to accurately and automatically identify the events and states from SMFS experiments with a machine learning approach, which combines clustering and classification for event identification of SMFS (ACCESS). As demonstrated by analysis of a series of data sets, ACCESS can extract the rupture forces from FECs containing multiple unfolding steps and classify the rupture forces into the corresponding conformational transitions. Moreover, ACCESS successfully identifies the unfolded and folded states even though the ETTs display severe nonmonotonic baseline drift. Besides, ACCESS is straightforward in use as it requires only three easy-to-interpret parameters. As such, we anticipate that ACCESS will be a useful, easy-to-implement and high-performance tool for event and state identification across a range of single-molecule experiments.
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    Impact of individual behavior adoption heterogeneity on epidemic transmission in multiplex networks
    Liang'an Huo(霍良安) and Yue Yu(于跃)
    2023 (10):  108703-108703.  doi: 10.1088/1674-1056/acea65
    摘要 ( 123 )   HTML ( 0 )   PDF(3956KB) ( 39 )  
    In recent years, the impact of information diffusion and individual behavior adoption patterns on epidemic transmission in complex networks has received significant attention. In the immunization behavior adoption process, different individuals often make behavioral decisions in different ways, and it is of good practical importance to study the influence of individual heterogeneity on the behavior adoption process. In this paper, we propose a three-layer coupled model to analyze the process of co-evolution of official information diffusion, immunization behavior adoption and epidemic transmission in multiplex networks, focusing on individual heterogeneity in behavior adoption patterns. Specifically, we investigate the impact of the credibility of social media and the risk sensitivity of the population on behavior adoption in further study of the effect of heterogeneity of behavior adoption on epidemic transmission. Then we use the microscopic Markov chain approach to describe the dynamic process and capture the evolution of the epidemic threshold. Finally, we conduct extensive simulations to prove our findings. Our results suggest that enhancing the credibility of social media can raise the epidemic transmission threshold, making it effective at controlling epidemic transmission during the dynamic process. In addition, improving an individuals' risk sensitivity, and thus their taking effective protective measures, can also reduce the number of infected individuals and delay the epidemic outbreak. Our study explores the role of individual heterogeneity in behavior adoption in real networks, more clearly models the effect of the credibility of social media and risk sensitivity of the population on the epidemic transmission dynamic, and provides a useful reference for managers to formulate epidemic control and prevention policies.
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    Influence of viscous force on the dynamic process of micro-sphere in optical tweezers
    Jing Liu(刘静), Xingyu Wu(吴星宇), Yimin Feng(冯怡敏), Mian Zheng(郑冕), and Zhiyuan Li(李志远)
    2023 (10):  108704-108704.  doi: 10.1088/1674-1056/acddd1
    摘要 ( 188 )   HTML ( 0 )   PDF(3893KB) ( 122 )  
    With the advantages of noncontact, high accuracy, and high flexibility, optical tweezers hold huge potential for micro-manipulation and force measurement. However, the majority of previous research focused on the state of the motion of particles in the optical trap, but paid little attention to the early dynamic process between the initial state of the particles and the optical trap. Note that the viscous forces can greatly affect the motion of micro-spheres. In this paper, based on the equations of Newtonian mechanics, we investigate the dynamics of laser-trapped micro-spheres in the surrounding environment with different viscosity coefficients. Through the calculations, over time the particle trajectory clearly reveals the subtle details of the optical capture process, including acceleration, deceleration, turning, and reciprocating oscillation. The time to equilibrium mainly depends on the corresponding damping coefficient of the surrounding environment and the oscillation frequency of the optical tweezers. These studies are essential for understanding various mechanisms to engineer the mechanical motion behavior of molecules or microparticles in liquid or air.
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    Corrigendum to “Reactive oxygen species in plasma against E. coli cells survival rate”
    Renwu Zhou(周仁武), Xianhui Zhang(张先徽), Zichao Zong(宗子超), Junxiong Li(李俊雄), Zhoubin Yang(杨周斌), Dongping Liu(刘东平), and Size Yang(杨思泽)
    2023 (10):  109901-109901.  doi: 10.1088/1674-1056/acfb7b
    摘要 ( 115 )   HTML ( 0 )   PDF(1495KB) ( 19 )  
    Recently, we found some errors in Fig. 3 of the article Chin. Phys. B 24 085201 (2015). Upon a thorough examination of the raw data materials, we confirm that the image error did not impact any of the findings and conclusions of the paper. Based on this, we have made corrections to the original article.
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