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11 November 2022, Volume 31 Issue 12 Previous issue    Next issue

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TOPICAL REVIEW—Celebrating 30 Years of Chinese Physics B

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Editorial: Celebrating the 30 Wonderful Year Journey of Chinese Physics B Hong-Jun Gao(高鸿钧), and Qihua Xiong(熊启华) Chin. Phys. B, 2022, 31 (12):  120101.  DOI: 10.1088/1674-1056/acaa95 Abstract ( 398 )   HTML ( 13 )   PDF (195KB) ( 472 )   The year 2022 marks the 30th anniversary of Chinese Physics B. This editorial provides a brief history of the journal and introduces the anniversary theme collection comprising over 30 invited reviews and perspective articles from renowned scholars in various branches of physics.

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Attosecond spectroscopy for filming the ultrafast movies of atoms, molecules and solids Lixin He(何立新), Xiaosong Zhu(祝晓松), Wei Cao(曹伟), Pengfei Lan(兰鹏飞), and Peixiang Lu(陆培祥) Chin. Phys. B, 2022, 31 (12):  123301.  DOI: 10.1088/1674-1056/aca6d2 Abstract ( 470 )   HTML ( 8 )   PDF (12045KB) ( 366 )   Three decades ago, a highly nonlinear nonpertubative phenomenon, now well-known as the high harmonic generation (HHG), was discovered when intense laser irradiates gaseous atoms. As the HHG produces broadband coherent radiation, it becomes the most promising source to obtain attosecond pulses. The door to the attosecond science was opened ever since. In this review, we will revisit the incredible adventure to the attoworld. Firstly, the progress of attosecond pulse generation is outlined. Then, we introduce the efforts on imaging the structures or filming the ultrafast dynamics of nuclei and electrons with unprecedented attosecond temporal and Angstrom spatial resolutions, utilizing the obtained attosecond pulses as well as the high harmonic spectrum itself.

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Advances of phononics in 2012—2022 Ya-Fei Ding(丁亚飞), Gui-Mei Zhu(朱桂妹), Xiang-Ying Shen(沈翔瀛),Xue Bai(柏雪), and Bao-Wen Li(李保文) Chin. Phys. B, 2022, 31 (12):  126301.  DOI: 10.1088/1674-1056/ac935d Abstract ( 450 )   HTML ( 10 )   PDF (3132KB) ( 306 )   Due to its great potential applications in thermal management, heat control, and quantum information, phononics has gained increasing attentions since the first publication in Rev. Mod. Phys. 84 1045 (2012). Many theoretical and experimental progresses have been achieved in the past decade. In this paper, we first give a critical review of the progress in thermal diodes and transistors, especially in classical regime. Then, we give a brief introduction to the new developing research directions such as topological phononics and quantum phononics. In the third part, we discuss the potential applications. Last but not least, we point out the outlook and challenges ahead.

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Molecular beam epitaxy growth of quantum devices Ke He(何珂) Chin. Phys. B, 2022, 31 (12):  126804.  DOI: 10.1088/1674-1056/aca6d3 Abstract ( 426 )   HTML ( 3 )   PDF (1803KB) ( 289 )   The inherent fragility and surface/interface-sensitivity of quantum devices demand fabrication techniques under very clean environment. Here, I briefly introduces several techniques based on molecular beam epitaxy growth on pre-patterned substrates which enable us to directly prepare in-plane nanostructures and heterostructures in ultrahigh vacuum. The molecular beam epitaxy-based fabrication techniques are especially useful in constructing the high-quality devices and circuits for solid-state quantum computing in a scalable way.

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A sport and a pastime: Model design and computation in quantum many-body systems Gaopei Pan(潘高培), Weilun Jiang(姜伟伦), and Zi Yang Meng(孟子杨) Chin. Phys. B, 2022, 31 (12):  127101.  DOI: 10.1088/1674-1056/aca083 Abstract ( 424 )   HTML ( 4 )   PDF (6474KB) ( 390 )   We summarize the recent developments in the model design and computation for a few representative quantum many-body systems, encompassing quantum critical metals beyond the Hertz-Millis-Moriya framework with pseudogap and superconductivity, SYK non-Fermi-liquid with self-tuned quantum criticality and fluctuation induced superconductivity, and the flat-band quantum Moiré lattice models in continuum where the interplay of quantum geometry of flat-band wave function and the long-range Coulomb interactions gives rise to novel insulating phases at integer fillings and superconductivity away from them. Although the narrative choreography seems simple, we show how important the appropriate model design and their tailor-made algorithmic developments - in other words, the scientific imagination inspired by the corresponding fast experimental developments in the aforementioned systems - compel us to invent and discover new knowledge and insights in the sport and pastime of quantum many-body research.

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Research progress of Pt and Pt-based cathode electrocatalysts for proton-exchange membrane fuel cells Ni Suo(索妮), Longsheng Cao(曹龙生), Xiaoping Qin(秦晓平), and Zhigang Shao(邵志刚) Chin. Phys. B, 2022, 31 (12):  128108.  DOI: 10.1088/1674-1056/aca081 Abstract ( 393 )   HTML ( 4 )   PDF (4748KB) ( 205 )   Proton-exchange membrane fuel cells (PEMFCs) have been widely used commercially to solve the energy crisis and environmental pollution. The oxygen reduction reaction (ORR) at the cathode is the rate-determining step in PEMFCs. Platinum (Pt) catalysts are used to accelerate the ORR kinetics. Pt's scarcity, high cost, and instability in an acidic environment at high potentials seriously hinder the commercialization of PEMFCs. Therefore, studies should explore electrocatalysts with high catalytic activity, enhanced stability, and low-Pt loading. This review briefly introduces the research progress on Pt and Pt-based ORR electrocatalysts for PEMFCs, including anticorrosion catalyst supports, Pt, and Pt-based alloy electrocatalysts. Advanced preparation technology and material characterization of Pt-based ORR electrocatalysts are necessary to improve the performance and corresponding reaction mechanisms.

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Single-molecular methodologies for the physical biology of protein machines Shuang Wang(王爽), Ying Lu(陆颖), and Ming Li(李明) Chin. Phys. B, 2022, 31 (12):  128702.  DOI: 10.1088/1674-1056/ac98a2 Abstract ( 364 )   HTML ( 3 )   PDF (5227KB) ( 235 )   Physical biology is an interdisciplinary field that bridges biology with physical sciences and engineering. Single-molecule physical biology focuses on dynamics of individual biomolecules and complexes, aiming to answering basic questions about their functions and mechanisms. It takes advantages of physical methodologies to gain quantitative understanding of biological processes, often engaging precise physical measurements of reconstructed objects to avoid interference from unnecessary complications. In this review, we (i) briefly introduce concepts of single-molecule physical biology, (ii) describe extensively used single-molecule methodologies that have been developed to address key questions in two important objects of single-molecule physical biology, namely, nucleic acid-interacting proteins and membrane-interacting proteins, and (iii) show by a few successful examples how one may use single-molecule methods to deepen our understanding of protein machines.

TOPICAL REVIEW—The third carbon: Carbyne with one-dimensional sp-carbon

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A review of arc-discharge method towards large-scale preparation of long linear carbon chains Yi-Fan Zhang(张一帆) Chin. Phys. B, 2022, 31 (12):  125201.  DOI: 10.1088/1674-1056/ac833f Abstract ( 428 )   HTML ( 16 )   PDF (3832KB) ( 277 )   Linear carbon chains as new one-dimensional (1D) nanomaterials attract attention for the predicted outstanding properties. However, the high reactivity of linear carbon chains hampers further experimental research. To date, different methods have been developed to synthesize new materials containing linear carbon chains. Among them, the arc-discharge method is a practical way to prepare both finite and infinite linear carbon chains. This review provides a brief discussion of the recent progress in the techniques to prepare carbon chain-based materials and then focuses on the arc-discharge method. The configuration of apparatus, optimal conditions, and the corresponding mechanism of arc-discharge method to prepare long linear carbon chain inside multi-walled carbon nanotubes are summarized in detail. The characterization techniques are introduced to evaluate the quality of products. Moreover, remaining challenges and perspectives are presented for further investigation of long linear carbon chains.

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Pulsed laser ablation in liquid of sp-carbon chains: Status and recent advances Pietro Marabotti, Sonia Peggiani, Alessandro Vidale, and Carlo Spartaco Casari Chin. Phys. B, 2022, 31 (12):  125202.  DOI: 10.1088/1674-1056/ac81b2 Abstract ( 274 )   HTML ( 9 )   PDF (6665KB) ( 141 )   This review provides a discussion of the current state of research on sp-carbon chains synthesized by pulsed laser ablation in liquid. In recent years, pulsed laser ablation in liquid (PLAL) has been widely employed for polyynes synthesis thanks to its flexibility with varying laser parameters, solvents, and targets. This allows the control of sp-carbon chains properties as yield, length, termination and stability. Although many reviews related to PLAL have been published, a comprehensive work reporting the current status and advances related to the synthesis of sp-carbon chains by PLAL is still missing. Here we first review the principle of PLAL and the mechanisms of formation of sp-carbon chains. Then we discuss the role of laser fluence (i.e. energy density), solvent, and target for sp-carbon chains synthesis. Lastly, we report the progress related to the prolonged stability of sp-carbon chains by PLAL encapsulated in polymeric matrices. This review will be a helpful guide for researchers interested in synthesizing sp-carbon chains by PLAL.

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Raman spectroscopy of isolated carbyne chains confined in carbon nanotubes: Progress and prospects Johannes M. A. Lechner, Pablo Hernández López, and Sebastian Heeg Chin. Phys. B, 2022, 31 (12):  127801.  DOI: 10.1088/1674-1056/ac9608 Abstract ( 356 )   HTML ( 9 )   PDF (4231KB) ( 200 )   Carbyne is an infinitely long linear chain of carbon atoms with sp1 hybridization and the truly one-dimensional allotrope of carbon. While obtaining freestanding carbyne is still an open challenge, the study of confined carbyne, linear chains of carbon encapsulated in carbon nanotubes, provides a pathway to explore carbyne and its remarkable properties in a well-defined environment. In this review, we discuss the basics and recent advances in studying single confined carbyne chains by Raman spectroscopy, which is their primary spectroscopic characterization method. We highlight where single carbyne chain studies are needed to advance our understanding of confined carbyne as a material system and provide an overview of the open questions that need to be addressed and of those aspects currently under debate.

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On-surface synthesis of one-dimensional carbyne-like nanostructures with sp-carbon Wenze Gao(高文泽), Chi Zhang(张弛), Zheng Zhou(周正), and Wei Xu(许维) Chin. Phys. B, 2022, 31 (12):  128101.  DOI: 10.1088/1674-1056/ac7f90 Abstract ( 384 )   HTML ( 8 )   PDF (4891KB) ( 256 )   Carbyne is an infinite one-dimensional carbon chain comprising of sp-hybridized carbons. Due to its high chemical reactivity and extreme instability, the synthesis and structural diversity of carbyne have been much less investigated in the past decades compared to carbon allotropes built with sp2 hybridized carbons, such as fullerenes, carbon nanotubes, and graphene. The emerging on-surface synthesis strategy provides an extremely promising approach for the fabrication of novel carbyne-like nanostructures with atomic precision. Herein, we summarize recent exciting progress in the synthesis of carbyne-like nanostructures with one-dimensional sp-carbon on surfaces, including polyynes, cumulenes, and organometallic polyynes. We also point out the scientific challenges and prospects, encouraging scientists to explore the fabrication and characterization of single strands of carbyne in this young and promising research field.

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One-dimensional sp carbon: Synthesis, properties, and modifications Chao-Fan Lv(吕超凡), Xi-Gui Yang(杨西贵), and Chong-Xin Shan(单崇新) Chin. Phys. B, 2022, 31 (12):  128103.  DOI: 10.1088/1674-1056/ac872f Abstract ( 309 )   HTML ( 12 )   PDF (17889KB) ( 322 )   Carbyne, as the truly one-dimensional carbon allotrope with sp-hybridization, has attracted significant interest in recent years, showing potential applications in next-generation molecular devices due to its ultimate one-atom thinness. Various excellent properties of carbyne have been predicted, however, free-standing carbyne sample is extremely unstable and the corresponding experimental researches and modifications are under-developed compared to other known carbon allotropes. The synthesis of carbyne has been slowly developed for the past decades. Recently, there have been several breakthroughs in in-situ synthesis and measurement of carbyne related materials, as well as the preparation of ultra-long carbon chains toward infinite carbyne. These progresses have aroused widespread discussion in the academic community. In this review, the latest approaches in the synthesis of sp carbon are summarized. We then discuss its extraordinary properties, including mechanical, electronic, magnetic, and optical properties, especially focusing on the regulations of these properties. Finally, we provide a perspective on the development of carbyne.

SPECIAL TOPIC—The third carbon: Carbyne with one-dimensional sp-carbon

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Chemical bonding in representative astrophysically relevant neutral, cation, and anion HCnH chains Ioan Baldea Chin. Phys. B, 2022, 31 (12):  123101.  DOI: 10.1088/1674-1056/ac9b04 Abstract ( 269 )   HTML ( 3 )   PDF (6583KB) ( 265 )   Most existing studies assign a polyynic and cumulenic character of chemical bonding in carbon-based chains relying on values of the bond lengths. Building on our recent work, in this paper we add further evidence on the limitations of such an analysis and demonstrate the significant insight gained via natural bond analysis. Presently reported results include atomic charges, natural bond order and valence indices obtained from ab initio computations for representative members of the astrophysically relevant neutral and charged HC2k/2k+1H chain family. They unravel a series of counter-intuitive aspects and/or help naive intuition in properly understanding microscopic processes, e.g., electron removal from or electron attachment to a neutral chain. Demonstrating that the Wiberg indices adequately quantify the chemical bonding structure of the HC2k/2k+1H chains—while the often heavily advertised Mayer indices do not—represents an important message conveyed by the present study.

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Nitrogen-tailored quasiparticle energy gaps of polyynes Kan Zhang(张侃), Jiling Li(李继玲), Peitao Liu(刘培涛), Guowei Yang(杨国伟), and Lei Shi(石磊) Chin. Phys. B, 2022, 31 (12):  123102.  DOI: 10.1088/1674-1056/ac8cde Abstract ( 295 )   HTML ( 5 )   PDF (1745KB) ( 209 )   Polyyne, an sp1-hybridized linear allotrope of carbon, has a tunable quasiparticle energy gap, which depends on the terminated chemical ending groups as well as the chain length. Previously, nitrogen doping was utilized to tailor the properties of different kinds of allotrope of carbon. However, how the nitrogen doping tailors the properties of the polyyne remains unexplored. Here, we applied the GW method to study the quasiparticle energy gaps of the N-doped polyynes with different lengths. When a C atom is substituted by an N atom in a polyyne, the quasiparticle energy gap varies with the substituted position in the polyyne. The modification is particularly pronounced when the second-nearest-neighboring carbon atom of a hydrogen atom is substituted. In addition, the nitrogen doping makes the Fermi level closer to the lowest unoccupied molecular orbital, resulting in an n-type semiconductor. Our results suggest another route to tailor the electronic properties of polyyne in addition to the length of polyyne and the terminated chemical ending groups.

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Accurate theoretical evaluation of strain energy of all-carboatomic ring (cyclo[2n]carbon), boron nitride ring, and cyclic polyacetylene Tian Lu(卢天), Zeyu Liu(刘泽玉), and Qinxue Chen(陈沁雪) Chin. Phys. B, 2022, 31 (12):  126101.  DOI: 10.1088/1674-1056/ac873a Abstract ( 387 )   HTML ( 5 )   PDF (2910KB) ( 132 )   Cyclocarbon fully consists of sp-hybridized carbon atoms, which shows quite unusual electronic and geometric structures compared to common molecules. In this work, we systematically studied strain energy (SE) of cyclocarbons of different sizes using regression analysis method based on electronic energies evaluated at the very accurate DLPNO-CCSD(T)/cc-pVTZ theoretical level. In addition, ring strain of two systems closely related to cyclocarbon, boron nitride (BN) ring, and cyclic polyacetylene (c-PA), is also explored. Very ideal relationships between SE and number of repeat units ($n)$ are built for cyclo[2$n$]carbon, B$_{n}$N$_{n}$, and [2$n$]c-PA as ${\rm SE} = 555.0\cdot n^{-1}$, 145.1$\cdot n^{-1}$, and 629.8$\cdot n^{-1}$ kcal$\cdot $mol$^{-1}$, respectively, and the underlying reasons of the difference and similarity in their SEs are discussed from electronic structure perspective. In addition, force constant of harmonic potential of C-C-C angles in cyclocarbon is derived based on SE values, the result is found to be 56.23 kcal$\cdot $mol$^{-1}\cdot $rad$^{-2}$. The possibility of constructing homodesmotic reactions to calculate SEs of cyclocarbons is also explored in this work, although this method is far less rigorous than the regression analysis method, its result is qualitatively correct and has the advantage of much lower computational cost. In addition, comparisons show that $\omega $B97XD/def2-TZVP is a good inexpensive alternative to the DLPNO-CCSD(T)/cc-pVTZ for evaluating energies used in deriving SE, while the popular and very cheap B3LYP/6-31G(d) level should be used with caution for systems with global electron conjugation such as c-PA.

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Large-scale synthesis of polyynes with commercial laser marking technology Liang Fang(房良), Yanping Xie(解燕平), Shujie Sun(孙书杰), and Wei Zi(訾威) Chin. Phys. B, 2022, 31 (12):  126803.  DOI: 10.1088/1674-1056/ac7cd1 Abstract ( 411 )   HTML ( 9 )   PDF (3057KB) ( 168 )   The space-confined synthesis method has been an efficient way for the preparation of linear carbon chains. However, the large-scale preparation of linear carbon chains still faces many challenges due to the lack of methods for the large-scale synthesis of precursors, such as short carbon chains (polyynes), and regulation technology for the transport of reactants in one-dimensional space. Here, we report a facile method for the rapid preparation of polyynes in large quantities using a commercial laser marking machine. Spectroscopic characterizations show that a large number of polyynes, such as C8H2, C10H2, C12H2, and C14H2, can be produced by ablating the graphite plate immersed in the organic liquid using a laser marking machine. The results of in situ Raman spectroscopy investigation of C2nH2-filled single-walled carbon nanotubes further confirm that a variety of polyyne molecules are synthesized. Meanwhile, in situ Raman spectroscopy also shows that the local heating treatment can accelerate the filling process of C2nH2 into one-dimensional channels. This work provides new insights into the study of linear carbon chains and space-confined synthesis methods.

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Conformational change-modulated spin transport at single-molecule level in carbon systems Yandong Guo(郭艳东), Xue Zhao(赵雪), Hongru Zhao(赵鸿儒), Li Yang(杨丽), Liyan Lin(林丽艳), Yue Jiang(姜悦), Dan Ma(马丹), Yuting Chen(陈雨婷), and Xiaohong Yan(颜晓红) Chin. Phys. B, 2022, 31 (12):  127201.  DOI: 10.1088/1674-1056/ac872d Abstract ( 379 )   HTML ( 9 )   PDF (1451KB) ( 159 )   Controlling the spin transport at the single-molecule level, especially without the use of ferromagnetic contacts, becomes a focus of research in spintronics. Inspired by the progress on atomic-level molecular synthesis, through first-principles calculations, we investigate the spin-dependent electronic transport of graphene nanoflakes with side-bonded functional groups, contacted by atomic carbon chain electrodes. It is found that, by rotating the functional group, the spin polarization of the transmission at the Fermi level could be switched between completely polarized and unpolarized states. Moreover, the transition between spin-up and spin-down polarized states can also be achieved, operating as a dual-spin filter. Further analysis shows that, it is the spin-dependent shift of density of states, caused by the rotation, that triggers the shift of transmission peaks, and then results in the variation of spin polarization. Such a feature is found to be robust to the length of the nanoflake and the electrode material, showing great application potential. Those findings may throw light on the development of spintronic devices.

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Extraordinary mechanical performance in charged carbyne Yong-Zhe Guo(郭雍哲), Yong-Heng Wang(汪永珩), Kai Huang(黄凯), Hao Yin(尹颢), and En-Lai Gao(高恩来) Chin. Phys. B, 2022, 31 (12):  128102.  DOI: 10.1088/1674-1056/ac7bf8 Abstract ( 395 )   HTML ( 12 )   PDF (9253KB) ( 249 )   Carbyne, the linear chain of carbon, promises the strongest and toughest material but possesses a Peierls instability (alternating single-bonds and triple-bonds) that reduces its strength and toughness. Herein, we computationally found that the gravimetric strength, strain-to-failure, and gravimetric toughness can be improved from 74 GPa·g-1·cm3, 18%, and 9.4 kJ·g-1 for pristine carbyne to the highest values of 106 GPa·g-1·cm3, 26%, and 19.0 kJ·g-1 for carbyne upon hole injection of +0.07 e/atom, indicating the charged carbyne with record-breaking mechanical performance. Based on the analyses of the atomic and electronic structures, the underlying mechanism behind the record-breaking mechanical performance was revealed as the suppressed and even eliminated bond alternation of carbyne upon charge injection.

INSTRUMENTATION AND MEASUREMENT

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Development of a cryogen-free dilution refrigerator Zhongqing Ji(姬忠庆), Jie Fan(樊洁), Jing Dong(董靖), Yongbo Bian(边勇波), and Zhi-Gang Cheng(程智刚) Chin. Phys. B, 2022, 31 (12):  120703.  DOI: 10.1088/1674-1056/ac9042 Abstract ( 579 )   HTML ( 8 )   PDF (1053KB) ( 658 )   With thermal fluctuation strongly suppressed, low temperature environment is essential for studies of condensed matter physics and developments of quantum technologies. Ultra-low temperature below 20 mK has demonstrated its importance and significance in physical sciences and information techniques. Dilution refrigeration is by far the best feasible and reliable method to generate and keep lattice temperature in this range. With a potential shortage of helium supply, cryogen-free dilution refrigerator (CFDR), eliminating the necessity of regular helium refill, becomes the main facility for the purpose of creating ultralow temperature environments. Here we describe our successful construction of a CFDR which reached a base temperature of around 10.9 mK for continuous circulation and 8.6 mK for single-shot operation. We describe its operating mechanism and the designs of key components, especially some unique designs including heat switch and alumina thermal link. Possible improvements in the future are also discussed.

DATA PAPER

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Electron excitation processes in low energy collisions of hydrogen-helium atoms Kun Wang(王堃), Chuan Dong(董川), Yi-Zhi Qu(屈一至), Ling Liu(刘玲), Yong Wu(吴勇),Xu-Hai Hong(洪许海), and Robert J. Buenker Chin. Phys. B, 2022, 31 (12):  123401.  DOI: 10.1088/1674-1056/aca14c Abstract ( 399 )   HTML ( 1 )   PDF (603KB) ( 242 )   The electron excitation processes of $\rm H(1s) + He(1s^{2}) \to H(2s/2p) + He(1s^{2})$ are studied in impact energy range of 20—2000 eV/u by using the quantum-mechanical molecular orbital close-coupling (QMOCC) method. Total and state-selective cross sections have been obtained and compared with the available theoretical and experimental results. The results agree well with available measurements in the overlapping energy regions overall. The comparison of our results with other theoretical calculations further demonstrates the importance of considering a sufficient number of channels. The datasets presented in this paper, including the excitation cross sections, are openly available at https://www.doi.org/10.57760/sciencedb.j00113.00083.

RAPID COMMUNICATION

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Learning physical states of bulk crystalline materials from atomic trajectories in molecular dynamics simulation Hot! Tian-Shou Liang(梁添寿), Peng-Peng Shi(时朋朋), San-Qing Su(苏三庆), and Zhi Zeng(曾志) Chin. Phys. B, 2022, 31 (12):  126402.  DOI: 10.1088/1674-1056/ac98a4 Abstract ( 475 )   HTML ( 1 )   PDF (3493KB) ( 244 )   Melting of crystalline material is a common physical phenomenon, yet it remains elusive owing to the diversity in physical pictures. In this work, we proposed a deep learning architecture to learn the physical states (solid- or liquid-phase) from the atomic trajectories of the bulk crystalline materials with four typical lattice types. The method has ultra-high accuracy (higher than 95%) for the classification of solid-liquid atoms during the phase transition process and is almost insensitive to temperature. The atomic physical states are identified from atomic behaviors without considering any characteristic threshold parameter, which yet is necessary for the classical methods. The phase transition of bulk crystalline materials can be correctly predicted by learning from the atomic behaviors of different materials, which confirms the close correlation between atomic behaviors and atomic physical states. These evidences forecast that there should be a more general undiscovered physical quantity implicated in the atomic behaviors and elucidate the nature of bulk crystalline melting.

GENERAL

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Reciprocal transformations of the space-time shifted nonlocal short pulse equations Jing Wang(王静), Hua Wu(吴华), and Da-Jun Zhang(张大军) Chin. Phys. B, 2022, 31 (12):  120201.  DOI: 10.1088/1674-1056/ac673b Abstract ( 355 )   HTML ( 1 )   PDF (837KB) ( 93 )   Reciprocal transformations of the space-time shifted nonlocal short pulse equations are elaborated. Covariance of dependent and independent variables involved in the reciprocal transformations is investigated. Exact solutions of the space-time shifted nonlocal short pulse equations are given in terms of double Wronskians. Realness of independent variables involved in the reciprocal transformations is verified. Dynamics of some obtained solutions are illustrated.

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Rogue waves of a (3+1)-dimensional BKP equation Yu-Qiang Yuan(袁玉强), Xiao-Yu Wu(武晓昱), and Zhong Du(杜仲) Chin. Phys. B, 2022, 31 (12):  120202.  DOI: 10.1088/1674-1056/ac6869 Abstract ( 429 )   HTML ( 3 )   PDF (3006KB) ( 157 )   We investigate certain rogue waves of a (3+1)-dimensional BKP equation via the Kadomtsev-Petviashili hierarchy reduction method. We obtain semi-rational solutions in the determinant form, which contain two special interactions: (i) one lump develops from a kink soliton and then fuses into the other kink one; (ii) a line rogue wave arises from the segment between two kink solitons and then disappears quickly. We find that such a lump or line rogue wave only survives in a short time and localizes in both space and time, which performs like a rogue wave. Furthermore, the higher-order semi-rational solutions describing the interaction between two lumps (one line rogue wave) and three kink solitons are presented.

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Sparse identification method of extracting hybrid energy harvesting system from observed data Ya-Hui Sun(孙亚辉), Yuan-Hui Zeng(曾远辉), and Yong-Ge Yang(杨勇歌) Chin. Phys. B, 2022, 31 (12):  120203.  DOI: 10.1088/1674-1056/ac9cbf Abstract ( 402 )   HTML ( 4 )   PDF (3811KB) ( 72 )   Hybrid energy harvesters under external excitation have complex dynamical behavior and the superiority of promoting energy harvesting efficiency. Sometimes, it is difficult to model the governing equations of the hybrid energy harvesting system precisely, especially under external excitation. Accompanied with machine learning, data-driven methods play an important role in discovering the governing equations from massive datasets. Recently, there are many studies of data-driven models done in aspect of ordinary differential equations and stochastic differential equations (SDEs). However, few studies discover the governing equations for the hybrid energy harvesting system under harmonic excitation and Gaussian white noise (GWN). Thus, in this paper, a data-driven approach, with least square and sparse constraint, is devised to discover the governing equations of the systems from observed data. Firstly, the algorithm processing and pseudo code are given. Then, the effectiveness and accuracy of the method are verified by taking two examples with harmonic excitation and GWN, respectively. For harmonic excitation, all coefficients of the system can be simultaneously learned. For GWN, we approximate the drift term and diffusion term by using the Kramers-Moyal formulas, and separately learn the coefficients of the drift term and diffusion term. Cross-validation (CV) and mean-square error (MSE) are utilized to obtain the optimal number of iterations. Finally, the comparisons between true values and learned values are depicted to demonstrate that the approach is well utilized to obtain the governing equations for the hybrid energy harvester under harmonic excitation and GWN.

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Variational quantum eigensolvers by variance minimization Dan-Bo Zhang(张旦波), Bin-Lin Chen(陈彬琳), Zhan-Hao Yuan(原展豪), and Tao Yin(殷涛) Chin. Phys. B, 2022, 31 (12):  120301.  DOI: 10.1088/1674-1056/ac8a8d Abstract ( 447 )   HTML ( 2 )   PDF (1223KB) ( 207 )   The original variational quantum eigensolver (VQE) typically minimizes energy with hybrid quantum-classical optimization that aims to find the ground state. Here, we propose a VQE based on minimizing energy variance and call it the variance-VQE, which treats the ground state and excited states on the same footing, since an arbitrary eigenstate for a Hamiltonian should have zero energy variance. We demonstrate the properties of the variance-VQE for solving a set of excited states in quantum chemistry problems. Remarkably, we show that optimization of a combination of energy and variance may be more efficient to find low-energy excited states than those of minimizing energy or variance alone. We further reveal that the optimization can be boosted with stochastic gradient descent by Hamiltonian sampling, which uses only a few terms of the Hamiltonian and thus significantly reduces the quantum resource for evaluating variance and its gradients.

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High-fidelity quantum sensing of magnon excitations with a single electron spin in quantum dots Le-Tian Zhu(朱乐天), Tao Tu(涂涛), Ao-Lin Guo(郭奥林), and Chuan-Feng Li(李传锋) Chin. Phys. B, 2022, 31 (12):  120302.  DOI: 10.1088/1674-1056/ac8919 Abstract ( 421 )   HTML ( 1 )   PDF (966KB) ( 155 )   Single-electron spins in quantum dots are the leading platform for qubits, while magnons in solids are one of the emerging candidates for quantum technologies. How to manipulate a composite system composed of both systems is an outstanding challenge. Here, we use spin-charge hybridization to effectively couple the single-electron spin state in quantum dots to the cavity and further to the magnons. Through this coupling, quantum dots can entangle and detect magnon states. The detection efficiency can reach 0.94 in a realistic experimental situation. We also demonstrate the electrical tunability of the scheme for various parameters. These results pave a practical pathway for applications of composite systems based on quantum dots and magnons.

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Measurement-device-independent one-step quantum secure direct communication Jia-Wei Ying(应佳伟), Lan Zhou(周澜), Wei Zhong(钟伟), and Yu-Bo Sheng(盛宇波) Chin. Phys. B, 2022, 31 (12):  120303.  DOI: 10.1088/1674-1056/ac8f37 Abstract ( 374 )   HTML ( 3 )   PDF (536KB) ( 72 )   The one-step quantum secure direct communication (QSDC) (Sci. Bull. 67, 367 (2022)) can effectively simplify QSDC's operation and reduce message loss. For enhancing its security under practical experimental condition, we propose two measurement-device-independent (MDI) one-step QSDC protocols, which can resist all possible attacks from imperfect measurement devices. In both protocols, the communication parties prepare identical polarization-spatial-mode two-photon hyperentangled states and construct the hyperentanglement channel by hyperentanglement swapping. The first MDI one-step QSDC protocol adopts the nonlinear-optical complete hyperentanglement Bell state measurement (HBSM) to construct the hyperentanglement channel, while the second protocol adopts the linear-optical partial HBSM. Then, the parties encode the photons in the polarization degree of freedom and send them to the third party for the hyperentanglement-assisted complete polarization Bell state measurement. Both protocols are unconditionally secure in theory. The simulation results show the MDI one-step QSDC protocol with complete HBSM attains the maximal communication distance of about 354 km. Our MDI one-step QSDC protocols may have potential applications in the future quantum secure communication field.

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Detecting the possibility of a type of photon number splitting attack in decoy-state quantum key distribution Xiao-Ming Chen(陈小明), Lei Chen(陈雷), and Ya-Long Yan(阎亚龙) Chin. Phys. B, 2022, 31 (12):  120304.  DOI: 10.1088/1674-1056/ac9b05 Abstract ( 378 )   HTML ( 1 )   PDF (475KB) ( 37 )   The existing decoy-state quantum key distribution (QKD) beating photon-number-splitting (PNS) attack provides a more accurate method to estimate the secure key rate, while it still considers that only single-photon pulses can generate secure keys in any case. However, multiphoton pulses can also generate secure keys if we can detect the possibility of PNS attack in the channel. The ultimate goal of this line of research is to confirm the absence of all types of PNS attacks. In particular, the PNS attack mentioned and detected in this paper is only the weaker version of PNS attack which significantly changes the observed values of the legitimate users. In this paper, under the null hypothesis of no weaker version of PNS attack, we first determine whether there is an attack or not by retrieving the missing information of the existing decoy-state protocols, extract a Cauchy distribution statistic, and further provide a detection method and the type I error probability. If the result is judged to be an attack, we can use the existing decoy-state method and the GLLP formula to estimate the secure key rate. Otherwise, the pulses with the same basis received including both single-photon pulses and multiphoton pulses, can be used to generate the keys and we give the secure key rate in this case. Finally, the associated experiments we performed (i.e., the significance level is 5%) show the correctness of our method.

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Quantum steerability of two qubits mediated by one-dimensional plasmonic waveguides Ye-Qi Zhang(张业奇), Xiao-Ting Ding(丁潇婷), Jiao Sun(孙娇), and Tian-Hu Wang(王天虎) Chin. Phys. B, 2022, 31 (12):  120305.  DOI: 10.1088/1674-1056/ac8af8 Abstract ( 388 )   HTML ( 1 )   PDF (702KB) ( 52 )   We study the dynamics of the quantum steering between two separated qubits trapped in a one-dimensional plasmonic waveguide. By numerical methods, we calculate the quantum steerability and other quantum correlations, i.e., entanglement, discord, and coherence, for both cases with and without laser driving fields. It is found that steerability may exhibit a sudden disappearance and sudden reappearance phenomenon. Specifically, there exist time windows with no steerability but finite entanglement. The effects of plasmon wavenumber and the distance between the two qubits on steerability are also examined. Furthermore, we show that quantum steerability is tunable by adjusting the laser driving fields.

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Magnetohydrodynamic Kelvin-Helmholtz instability for finite-thickness fluid layers Hong-Hao Dai(戴鸿昊), Miao-Hua Xu(徐妙华), Hong-Yu Guo(郭宏宇), Ying-Jun Li(李英骏), and Jie Zhang(张杰) Chin. Phys. B, 2022, 31 (12):  120401.  DOI: 10.1088/1674-1056/ac8924 Abstract ( 392 )   HTML ( 1 )   PDF (718KB) ( 107 )   We have derived the analytical formulas for the Kelvin-Helmholtz instability (KHI) of two superposed finite-thickness fluid layers with the magnetic field effect into consideration. The linear growth rate of KHI will be reduced when the thickness of the fluid with large density is decreased or the thickness of fluid with small density is increased. When the thickness and the magnetic field act together on the KHI, the effect of thickness is more obvious when the magnetic field intensity is weak. The magnetic field transition layer destabilizes (enforces) the KHI, especially in the case of small thickness of the magnetic field transition layer. When considering the effect of magnetic field, the linear growth rate of KHI always decreases after reaching the maximum with the increase of total thickness. The stronger the magnetic field intensity is, the more obvious the growth rate decreases with the total thickness. Thus, it should be included in applications where the effect of fluid thickness on the KHI cannot be ignored, such as in double-cone ignition scheme for inertial confinement fusion.

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A novel hyperchaotic map with sine chaotification and discrete memristor Qiankun Sun(孙乾坤), Shaobo He(贺少波), Kehui Sun(孙克辉), and Huihai Wang(王会海) Chin. Phys. B, 2022, 31 (12):  120501.  DOI: 10.1088/1674-1056/ac8f3a Abstract ( 420 )   HTML ( 1 )   PDF (7187KB) ( 265 )   Discrete memristor has become a hotspot since it was proposed recently. However, the design of chaotic maps based on discrete memristor is in its early research stage. In this paper, a memristive seed chaotic map is proposed by combining a quadratic discrete memristor with the sine function. Furthermore, by applying the chaotification method, we obtain a high-dimensional chaotic map. Numerical analysis shows that it can generate hyperchaos. With the increase of cascade times, the generated map has more positive Lyapunov exponents and larger hyperchaotic range. The National Institute of Standards and Technology (NIST) test results show that the chaotic pseudo-random sequence generated by cascading two seed maps has good unpredictability, and it indicates the potential in practical application.

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Resonance and antiresonance characteristics in linearly delayed Maryland model Hsinchen Yu(于心澄), Dong Bai(柏栋), Peishan He(何佩珊), Xiaoping Zhang(张小平), Zhongzhou Ren(任中洲), and Qiang Zheng(郑强) Chin. Phys. B, 2022, 31 (12):  120502.  DOI: 10.1088/1674-1056/ac7a0d Abstract ( 341 )   HTML ( 3 )   PDF (2798KB) ( 142 )   The Maryland model is a critical theoretical model in quantum chaos. This model describes the motion of a spin-1/2 particle on a one-dimensional lattice under the periodical disturbance of the external delta-function-like magnetic field. In this work, we propose the linearly delayed quantum relativistic Maryland model (LDQRMM) as a novel generalization of the original Maryland model and systematically study its physical properties. We derive the resonance and antiresonance conditions for the angular momentum spread. The "characteristic sum" is introduced in this paper as a new measure to quantify the sensitivity between the angular momentum spread and the model parameters. In addition, different topological patterns emerge in the LDQRMM. It predicts some additions to the Anderson localization in the corresponding tight-binding systems. Our theoretical results could be verified experimentally by studying cold atoms in optical lattices disturbed by a linearly delayed magnetic field.

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Measure synchronization in hybrid quantum-classical systems Haibo Qiu(邱海波), Yuanjie Dong(董远杰), Huangli Zhang(张黄莉), and Jing Tian(田静) Chin. Phys. B, 2022, 31 (12):  120503.  DOI: 10.1088/1674-1056/ac685c Abstract ( 287 )   HTML ( 0 )   PDF (1610KB) ( 33 )   Measure synchronization in hybrid quantum-classical systems is investigated in this paper. The dynamics of the classical subsystem is described by the Hamiltonian equations, while the dynamics of the quantum subsystem is governed by the Schrödinger equation. By increasing the coupling strength in between the quantum and classical subsystems, we reveal the existence of measure synchronization in coupled quantum-classical dynamics under energy conservation for the hybrid systems.

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Learnable three-dimensional Gabor convolutional network with global affinity attention for hyperspectral image classification Hai-Zhu Pan(潘海珠), Mo-Qi Liu(刘沫岐), Hai-Miao Ge(葛海淼), and Qi Yuan(袁琪) Chin. Phys. B, 2022, 31 (12):  120701.  DOI: 10.1088/1674-1056/ac8cd7 Abstract ( 374 )   HTML ( 0 )   PDF (4710KB) ( 76 )   Benefiting from the development of hyperspectral imaging technology, hyperspectral image (HSI) classification has become a valuable direction in remote sensing image processing. Recently, researchers have found a connection between convolutional neural networks (CNNs) and Gabor filters. Therefore, some Gabor-based CNN methods have been proposed for HSI classification. However, most Gabor-based CNN methods still manually generate Gabor filters whose parameters are empirically set and remain unchanged during the CNN learning process. Moreover, these methods require patch cubes as network inputs. Such patch cubes may contain interference pixels, which will negatively affect the classification results. To address these problems, in this paper, we propose a learnable three-dimensional (3D) Gabor convolutional network with global affinity attention for HSI classification. More precisely, the learnable 3D Gabor convolution kernel is constructed by the 3D Gabor filter, which can be learned and updated during the training process. Furthermore, spatial and spectral global affinity attention modules are introduced to capture more discriminative features between spatial locations and spectral bands in the patch cube, thus alleviating the interfering pixels problem. Experimental results on three well-known HSI datasets (including two natural crop scenarios and one urban scenario) have demonstrated that the proposed network can achieve powerful classification performance and outperforms widely used machine-learning-based and deep-learning-based methods.

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Detailed characterization of polycapillary focusing x-ray lenses by a charge-coupled device detector and a pinhole Xue-Peng Sun(孙学鹏), Shang-Kun Shao(邵尚坤), Hui-Quan Li(李惠泉), Tian-Yu Yuan(袁天语), and Tian-Xi Sun(孙天希) Chin. Phys. B, 2022, 31 (12):  120702.  DOI: 10.1088/1674-1056/ac8c3c Abstract ( 390 )   HTML ( 0 )   PDF (1311KB) ( 235 )   A method to measure the detailed performance of polycapillary x-ray optics by a pinhole and charge coupled device (CCD) detector was proposed in this study. The pinhole was located between the x-ray source and the polycapillary x-ray optics to determine the illuminating region of the incident x-ray beam on the input side of the optics. The CCD detector placed downstream of the polycapillary x-ray optics ensured that the incident x-ray beam controlled by the pinhole irradiated a specific region of the input surface of the optics. The intensity of the output beam of the polycapillary x-ray optics was obtained from the far-field image of the output beam of the optics captured by CCD detector. As an application example, the focal spot size, gain in power density, transmission efficiency, and beam divergence of different parts of a polycapillary focusing x-ray lenses (PFXRL) were measured by a pinhole and CCD detector. Three pinholes with diameters of 500, 1000, and 2000 μm were used to adjust the diameter of the incident x-ray beam illuminating the PFXRL from 500 μm to the entire surface of the input side of the PFXRL. The focal spot size of the PFXRL, gain in power density, transmission efficiency, and beam divergence ranged from 27.1 μm to 34.6 μm, 400 to 3460, 26.70% to 5.38%, and 16.8 mrad to 84.86 mrad, respectively.

ATOMIC AND MOLECULAR PHYSICS

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High resolution spectroscopy of Rb in magnetic field by far-detuning electromagnetically induced transparency Zi-Shan Xu(徐子珊), Han-Mu Wang(王汉睦), Ming-Hao Cai(蔡明皓), Shu-Hang You(游书航), and Hong-Ping Liu(刘红平) Chin. Phys. B, 2022, 31 (12):  123201.  DOI: 10.1088/1674-1056/ac6862 Abstract ( 360 )   HTML ( 0 )   PDF (1020KB) ( 138 )   We have presented a high resolution spectroscopy of Rb in magnetic field by far-detuning electromagnetically induced transparency (EIT). The EIT spectrum in the $\Xi$-type configuration is usually companied by a double resonance optical pumping (DROP) due to the strong optical coupling between the two upper states, leading to the spectral lines seriously deformed and widely broadened for complex relaxation processes in DROP. Here we demonstrate a high resolution spectroscopy by far-detuning EIT for $^{87}\rm{Rb}$ $\rm{5S_{1/2}\rightarrow5P_{3/2}\rightarrow5D_{5/2}}$ in magnetic fields. The method of far-detuning eliminates the relaxation in DROP to the most extent and decreases the spectral linewidth from more than 20 MHz down to its natural linewidth limit (6 MHz). The deformation of the spectral lines also disappears and the observed spectra are well in accordance with the theoretical calculation. Our work shows that far-detuning EIT is a reliable high resolution spectroscopic method when the relaxation in DROP cannot be neglected, especially for the case of transition to low excited states.

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Multiple collisions in crystal high-order harmonic generation Dong Tang(唐栋) and Xue-Bin Bian(卞学滨) Chin. Phys. B, 2022, 31 (12):  123202.  DOI: 10.1088/1674-1056/ac6b2c Abstract ( 332 )   HTML ( 2 )   PDF (2120KB) ( 70 )   We theoretically investigate high-order harmonic generation (HHG) in crystals induced by linearly polarized laser fields. We obtain the HHG spectra by solving the semiconductor Bloch equations and analyze the radiation process by different models. Here we propose a multiple collision model, in which the electrons and holes are produced at different times and places. It is found that the multiple collision trajectories can help us comprehensively and better explain the results of the quantum calculation. Moreover, we find that the harmonic suppression occurs due to the overlap of multiple collision trajectories.

ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS

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Transmission-type reconfigurable metasurface for linear-to-circular and linear-to-linear polarization conversions Ping Wang(王平), Yu Wang(王豫), Zhongming Yan(严仲明), and Hongcheng Zhou(周洪澄) Chin. Phys. B, 2022, 31 (12):  124201.  DOI: 10.1088/1674-1056/ac8ce0 Abstract ( 341 )   HTML ( 3 )   PDF (3915KB) ( 267 )   We present a transmission-type polarization conversion metamaterial (PCM) whose functions can be dynamically switched among the linear-to-circular (LTC) and linear-to-linear (LTL) polarization conversions. The proposed PCM consists of a grating, a polarization conversion surface and a reconfigurable polarization selective surface incorporated with PIN diodes. By changing the states of diodes, the PCM can achieve the reconfigurable manipulations for incident waves. The Fabry-Pérot (F-P) resonances excited by the PCM contribute to the polarization conversions, as is illustrated. Moreover, through establishing the F-P-like cavity model and analyzing the electric field components of the transmitted waves, the conditions for realizing LTC polarization conversion are revealed, which can guide the construction of PCM. The prototype of PCM is fabricated and measured, which can achieve LTC and LTL polarization conversions within 3.31-3.56 GHz and 2.76-4.24 GHz, respectively, the polarization conversion ratios of two functions are higher than 0.95. The measurement results are in agreement with the simulation data.

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Enhancing terahertz photonic spin Hall effect via optical Tamm state and the sensing application Jie Cheng(程杰), Jiahao Xu(徐家豪), Yinjie Xiang(项寅杰), Shengli Liu(刘胜利), Fengfeng Chi(迟逢逢), Bin Li(李斌), and Peng Dong(董鹏) Chin. Phys. B, 2022, 31 (12):  124202.  DOI: 10.1088/1674-1056/ac92d5 Abstract ( 333 )   HTML ( 1 )   PDF (1510KB) ( 106 )   The photonic spin Hall effect (PSHE), characterized by two splitting beams with opposite spins, has great potential applications in nano-photonic devices, optical sensing fields, and precision metrology. We present the significant enhancement of terahertz (THz) PSHE by taking advantage of the optical Tamm state (OTS) in InSb-distributed Bragg reflector (DBR) structure. The spin shift of reflected light can be dynamically tuned by the structural parameters (e.g. the thickness) of the InSb-DBR structure as well as the temperature, and the maximum spin shift for a horizontally polarized incident beam at 1.1 THz can reach up to 11.15 mm. Moreover, we propose a THz gas sensing device based on the enhanced PSHE via the strong excitation of OTS for the InSb-DBR structure with a superior intensity sensitivity of 5.873×104 mm/RIU and good stability. This sensor exhibits two orders of magnitude improvement compared with the similar PSHE sensor based on InSb-supported THz long-range surface plasmon resonance. These findings may provide an alternative way for the enhanced PSHE and offer the opportunity for developing new optical sensing devices.

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Watt-level, green-pumped optical parametric oscillator based on periodically poled potassium titanyl phosphate with high extraction efficiency Hot! Hang-Hang Yu(俞航航), Zhi-Tao Zhang(张志韬), and Hong-Wen Xuan(玄洪文) Chin. Phys. B, 2022, 31 (12):  124203.  DOI: 10.1088/1674-1056/ac8346 Abstract ( 480 )   HTML ( 0 )   PDF (1029KB) ( 248 )   We report a compact, efficient optical parametric oscillator (OPO) based on a periodically poled potassium titanyl phosphate (PPKTP) crystal pumped by a 532 nm laser, which generated 1.51 W of average power at the signal wavelength of 709 nm with the pulse duration of ～ 1.0 ns. The extraction efficiency was up to 59%. To the best of our knowledge, this is the first report on Watt-level green-pumped PPKTP-based singly resonant oscillator OPO (SRO-OPO). The precise build-up time of OPO was determined to be 1.6 ns benefitting from the characteristic of twin-peak pulse profile of pump beam. The spectrum width of the idler was also measured to be 4.2 nm with the central wavelength of 2134 nm at 0.2 nm spectral resolution of optical spectrum analyzer. In addition, the beam quality of M2 < 1.9 of generated signal exhibits a good consistency with M2 < 1.5 for the pump source.

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High-order harmonic generations in tilted Weyl semimetals Zi-Yuan Li(李子元), Qi Li(李骐), and Zhou Li(李舟) Chin. Phys. B, 2022, 31 (12):  124204.  DOI: 10.1088/1674-1056/ac9220 Abstract ( 363 )   HTML ( 0 )   PDF (1609KB) ( 179 )   We investigate high-order harmonic generations (HHGs) under comparison of Weyl cones in two types. Due to the hyperboloidal electron pocket structure, strong noncentrosymmetrical generations in high orders are observed around a single type-II Weyl point, especially at zero frequency. Such a remarkable DC signal is proved to have attributions from the intraband transition after spectral decomposition. Under weak pulse electric field, the linear optical response of a non-tilted Weyl cone is consistent with the Kubo theory. With extensive numerical simulations, we conclude that the non-zero chemical potential can enhance the even-order generations, from the slightly tilted system to the over-tilted systems. In consideration of dynamical symmetries, type-I and type-II Weyl cones also show different selective responses under the circularly polarized light. Finally, using a more realistic model containing two pairs of Weyl points, we demonstrate that paired Weyl points with opposite chirality can suppress the overall even-order generations.

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Single-frequency distributed Bragg reflector Tm:YAG ceramic derived all-glass fiber laser at 1.95 μm Guo-Quan Qian(钱国权), Min-Bo Wu(吴敏波), Guo-Wu Tang(唐国武), Min Sun(孙敏),Dong-Dan Chen(陈东丹), Zhi-Bin Zhang(张志斌), Hui Luo(罗辉), and Qi Qian(钱奇) Chin. Phys. B, 2022, 31 (12):  124205.  DOI: 10.1088/1674-1056/ac904c Abstract ( 415 )   HTML ( 0 )   PDF (692KB) ( 68 )   A 135 mW single-frequency distributed Bragg reflector fiber laser at 1.95 μm was obtained based on a Tm:YAG ceramic-derived all-glass fiber. The fiber laser achieved an optical signal-to-noise ratio of ～ 77 dB. Moreover, the threshold and linewidth of the single-frequency laser were measured to be 15.4 mW and 4.5 kHz, respectively. In addition, the measured relative intensity noise was less than -140 dB· Hz-1 at frequencies of over 10 MHz. The results show that the as-drawn Tm:YAG ceramic-derived all-glass fiber is highly promising for ～ 2 μm single-frequency fiber laser applications.

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Design of broadband achromatic metasurface device based on phase-change material Ge2Sb2Te5 Shuyuan Lv(吕淑媛), Xinhui Li(李新慧), Wenfeng Luo(罗文峰), and Jie Jia(贾洁) Chin. Phys. B, 2022, 31 (12):  124206.  DOI: 10.1088/1674-1056/ac657a Abstract ( 375 )   HTML ( 0 )   PDF (4166KB) ( 69 )   Based on the phase-change material Ge2Sb2Te5 (GST), achromatic metasurface optical device in the longer-infrared wavelength is designed. With the combination of the linear phase gradient GST nanopillar and the adjustment of the crystalline fraction m value of GST, the polarization insensitive achromic metalenses and beam deflector metasurface within the longer-infrared wavelength 9.5 μm to 13 μm are realized. The design results show that the achromatic metalenses can be focused on the same focal plane within the working waveband. The simulation calculation results show that the full-width at half-maximum (FWHM) of the focusing spot reaches the diffraction limit at each wavelength. In addition, the same method is also used to design a broadband achromatic beam deflector metasurface with the same deflection angle of 19°. The method proposed in this article not only provides new ideas for the design of achromatic metasurfaces, but also provides new possibilities for the integration of optical imaging, optical coding and other related optical systems.

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Asymmetrical photonic spin Hall effect based on dielectric metasurfaces Guangzhou Geng(耿广州), Ruhao Pan(潘如豪), Wei Zhu(朱维), and Junjie Li(李俊杰) Chin. Phys. B, 2022, 31 (12):  124207.  DOI: 10.1088/1674-1056/ac754b Abstract ( 369 )   HTML ( 0 )   PDF (1716KB) ( 131 )   The photonic spin Hall effect has attracted considerable research interest due to its potential applications in spin-controlled nanophotonic devices. However, realization of the asymmetrical photonic spin Hall effect with a single optical element is still a challenge due to the conjugation of the Pancharatnam-Berry phase, which reduces the flexibility in various applications. Here, we demonstrate an asymmetrical spin-dependent beam splitter based on a single-layer dielectric metasurface exhibiting strong and controllable optical response. The metasurface consists of an array of dielectric nanofins, where both varying rotation angles and feature sizes of the unit cells are utilized to create high-efficiency dielectric metasurfaces, which enables to break the conjugated characteristic of phase gradient. Thanks to the superiority of the phase modulation ability, when the fabricated metasurface is under normal incidence with a wavelength of 1550 nm, the left-handed circular polarization (LCP) light exhibits an anomalous refraction angle of 28.9°, while the right-handed circular polarization (RCP) light transmits directly. The method we proposed can be used for the flexible manipulation of spin photons and has potentials in high efficiency metasurfaces with versatile functionalities, especially with metasurfaces in a compact space.

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Sensitivity improvement of aluminum-based far-ultraviolet nearly guided-wave surface plasmon resonance sensor Tianqi Li(李天琦), Shujing Chen(陈淑静), and Chengyou Lin(林承友) Chin. Phys. B, 2022, 31 (12):  124208.  DOI: 10.1088/1674-1056/ac89e0 Abstract ( 401 )   HTML ( 0 )   PDF (1384KB) ( 49 )   An aluminum (Al) based nearly guided-wave surface plasmon resonance (NGWSPR) sensor is investigated in the far-ultraviolet (FUV) region. By simultaneously optimizing the thickness of Al and dielectric films, the sensitivity of the optimized Al-based FUV-NGWSPR sensor increases from 183°/RIU to 309°/RIU, and its figure of merit rises from 26.47 RIU-1 to 32.59 RIU-1 when the refractive index of dielectric increases from 2 to 5. Compared with a traditional FUV-SPR sensor without dielectric, the optimized FUV-NGWSPR sensor can realize simultaneous improvement of sensitivity and figure of merit. In addition, the FUV-NGWSPR sensor with realistic materials (diamond, Ta2O5, and GaN) is also investigated, and 137.84%, 52.70%, and 41.89% sensitivity improvements are achieved respectively. This work proposes a method for performance improvement of FUV-SPR sensors by exciting nearly guided-wave, and could be helpful for the high-performance SPR sensor in the short-wavelength region.

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Modulated spatial transmission signals in the photonic bandgap Wenqi Xu(许文琪), Hui Wang(王慧), Daohong Xie(谢道鸿), Junling Che(车俊岭), and Yanpeng Zhang(张彦鹏) Chin. Phys. B, 2022, 31 (12):  124209.  DOI: 10.1088/1674-1056/ac76b3 Abstract ( 326 )   HTML ( 0 )   PDF (1106KB) ( 43 )   This paper describes the spatial transmission of electromagnetically induced transparency and four-wave mixing signals in the photonic bandgap structure, which are modulated using the adjustable parameters of light fields. The spatial transmission patterns of the relevant signals are experimentally investigated with respect to the optical nonlinear Kerr effect that occurs in the modulation process. The experimental results reveal the spatial transmission patterns of the probe transmission and the four-wave mixing signals, such as focusing, defocusing, shifting, and spatial splitting. This study explains how the tunable parameters of light fields and their interactions with each other can regulate the spatial transmission of the light fields by changing the refractive indices of media, which provides a new research perspective and a degree of experimental technology support for more efficient all-optical communications.

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One-dimensional $\mathcal{PT}$-symmetric acoustic heterostructure Hai-Xiao Zhang(张海啸), Wei Xiong(熊威), Ying Cheng(程营), and Xiao-Jun Liu(刘晓峻) Chin. Phys. B, 2022, 31 (12):  124301.  DOI: 10.1088/1674-1056/ac90b3 Abstract ( 308 )   HTML ( 0 )   PDF (836KB) ( 167 )   The explorations of parity-time ($\mathcal{PT}$)-symmetric acoustics have resided at the frontier in physics, and the pre-existing accessing of exceptional points typically depends on Fabry-Perot resonances of the coupling interlayer sandwiched between balanced gain and loss components. Nevertheless, the concise $\mathcal{PT}$-symmetric acoustic heterostructure, eliminating extra interactions caused by the interlayer, has not been researched in depth. Here we derive the generalized unitary relation for one-dimensional (1D) $\mathcal{PT}$-symmetric heterostructure of arbitrary complexity, and demonstrate four disparate patterns of anisotropic transmission resonances (ATRs) accompanied by corresponding spontaneous phase transitions. As a special case of ATR, the occasional bidirectional transmission resonance reconsolidates the ATR frequencies that split when waves incident from opposite directions, whose spatial profiles distinguish from a unitary structure. The derived theoretical relation can serve as a predominant signature for the presence of $\mathcal{PT}$ symmetry and $\mathcal{PT}$-symmetry-breaking transition, which may provide substantial support for the development of prototype devices with asymmetric acoustic responses.

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Beam alignments based on the spectrum decomposition of orbital angular momentums for acoustic-vortex communications Gepu Guo(郭各朴), Xinjia Li(李昕珈), Qingdong Wang(王青东), Yuzhi Li(李禹志), Qingyu Ma(马青玉), Juan Tu(屠娟), and Dong Zhang(章东) Chin. Phys. B, 2022, 31 (12):  124302.  DOI: 10.1088/1674-1056/ac686a Abstract ( 379 )   HTML ( 0 )   PDF (1831KB) ( 121 )   Given the enhanced channel capacity of wave chirality, acoustic communications based on the orbital angular momentum (OAM) of acoustic-vortex (AV) beams are of significant interest for underwater data transmissions. However, the stringent beam alignment is required for the coaxial arrangement of transceiver arrays to ensure the accuracy and reliability of OAM decoding. To avoid the required multiple measurements of the traditional orthogonality based algorithm, the beam alignment algorithm based on the OAM spectrum decomposition is proposed for AV communications by using simplified ring-arrays. Numerical studies of the single-OAM and OAM-multiplexed AV beams show that the error of the OAM spectrum increases with the translation distance and the deflection angle of the transceiver arrays. To achieve an ideal arrangement, two methods of the single-array translation alignment and the dual-array deflection alignment are developed based on the least standard deviation of the OAM spectrum (SD-OAM). By decreasing the SD-OAM towards zero using transceiver arrays of 16 transmitters and 16 receivers, accurate beam alignments are accomplished by multiple adjustments in three dimensions. The proposed method is also demonstrated by experimental measurements of the OAM dispersion and the SD-OAM for misaligned beams. The results demonstrate the feasibility of the rapid beam alignment based on the OAM spectrum decomposition by using simplified transceiver ring-arrays, and suggest more application potentials for acoustic communications.

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Electromagnetic control of the instability in the liquid metal flow over a backward-facing step Ya-Dong Huang(黄亚冬), Jia-Wei Fu(付佳维), and Long-Miao Chen(陈龙淼) Chin. Phys. B, 2022, 31 (12):  124701.  DOI: 10.1088/1674-1056/ac989d Abstract ( 439 )   HTML ( 0 )   PDF (2850KB) ( 54 )   The tile-type electromagnetic actuator (TEA) and stripe-type electromagnetic actuator (SEA) are applied to the active control of the perturbation energy in the liquid metal flow over a backward-facing step (BFS). Three control strategies consisting of base flow control (BFC), linear model control (LMC) and combined model control (CMC) are considered to change the amplification rate of the perturbation energy. CMC is the combination of BFC and LMC. SEA is utilized in BFC to produce the streamwise Lorentz force thus adjusting the amplification rate via modifying the flow structures, and the magnitude of the maximum amplification rate could reach to 6 orders. TEA is used in LMC to reduce the magnitude of the amplification rate via the wall-normalwise Lorentz force, and the magnitude could be decreased by 2 orders. Both TEA and SEA are employed in CMC where the magnitude of the amplification rate could be diminished by 3 orders. In other words, the control strategy of CMC could capably alter the flow instability of the liquid metal flow.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Upgrade of the magnetic diagnostic system for restart of HT-6M operation Li-Xing Chen(陈力行), Biao Shen(沈飊), Da-Long Chen(陈大龙), Zheng-Ping Luo(罗正平),Zu-Chao Zhang(张祖超), Ying Chen(陈颖), Yong Wang(王勇), and Jin-Ping Qian(钱金平) Chin. Phys. B, 2022, 31 (12):  125203.  DOI: 10.1088/1674-1056/ac7f93 Abstract ( 385 )   HTML ( 0 )   PDF (2690KB) ( 140 )   The HT-6M tokamak at the Thailand Institute of Nuclear Technology has been restarted. In order to ensure the smooth breakdown of plasma and obtain plasma discharge parameters, optimization of the poloidal field coils and upgrade of the magnetic diagnostics are described in this article. A perfect null field (stray field in the main chamber < 10 G) is obtained using an ohmic heating field. To obtain important information about the plasma, an external magnetic diagnostics system is designed and calibrated, including a Rogowski coil (measuring plasma current), a magnetic probe (measuring external field), diamagnetic loops (measuring βp) and so on. In order to realize high-frequency signal measurement and transmission, a series of frequency responses with the magnetic probe and transmission line are tested. Later, to verify the null field, a fitting code is developed to reconstruct the stray field in the vacuum chamber based on magnetic probe measurements and flux loops. The results show that the error is within 1.5%. This indicates the accuracy of the magnetic measurement system and ensures the preparation for the breakdown of plasma.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Comparison of formation and evolution of radiation-induced defects in pure Ni and Ni-Co-Fe medium-entropy alloy Lin Lang(稂林), Huiqiu Deng(邓辉球), Jiayou Tao(陶家友), Tengfei Yang(杨腾飞), Yeping Lin(林也平), and Wangyu Hu(胡望宇) Chin. Phys. B, 2022, 31 (12):  126102.  DOI: 10.1088/1674-1056/ac891e Abstract ( 377 )   HTML ( 2 )   PDF (5563KB) ( 228 )   High-entropy alloys (HEAs) and medium-entropy alloys (MEAs) have attracted a great deal of attention for developing nuclear materials because of their excellent irradiation tolerance. Herein, formation and evolution of radiation-induced defects in NiCoFe MEA and pure Ni are investigated and compared using molecular dynamics simulation. It is observed that the defect recombination rate of ternary NiCoFe MEA is higher than that of pure Ni, which is mainly because, in the process of cascade collision, the energy dissipated through atom displacement decreases with increasing the chemical disorder. Consequently, the heat peak phase lasts longer, and the recombination time of the radiation defects (interstitial atoms and vacancies) is likewise longer, with fewer deleterious defects. Moreover, by studying the formation and evolution of dislocation loops in Ni-Co-Fe alloys and Ni, it is found that the stacking fault energy in Ni-Co-Fe decreases as the elemental composition increases, facilitating the formation of ideal stacking fault tetrahedron structures. Hence, these findings shed new light on studying the formation and evolution of radiation-induced defects in MEAs.

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Impact of incident direction on neutron-induced single-bit and multiple-cell upsets in 14 nm FinFET and 65 nm planar SRAMs Shao-Hua Yang(杨少华), Zhan-Gang Zhang(张战刚), Zhi-Feng Lei(雷志锋), Yun Huang(黄云), Kai Xi(习凯), Song-Lin Wang(王松林), Tian-Jiao Liang(梁天骄), Teng Tong(童腾), Xiao-Hui Li(李晓辉), Chao Peng(彭超), Fu-Gen Wu(吴福根), and Bin Li(李斌) Chin. Phys. B, 2022, 31 (12):  126103.  DOI: 10.1088/1674-1056/ac785a Abstract ( 424 )   HTML ( 2 )   PDF (2300KB) ( 79 )   Based on the BL09 terminal of China Spallation Neutron Source (CSNS), single event upset (SEU) cross sections of 14 nm fin field-effect transistor (FinFET) and 65 nm quad data rate (QDR) static random-access memories (SRAMs) are obtained under different incident directions of neutrons: front, back and side. It is found that, for both technology nodes, the "worst direction" corresponds to the case that neutrons traverse package and metallization before reaching the sensitive volume. The SEU cross section under the worst direction is 1.7-4.7 times higher than those under other incident directions. While for multiple-cell upset (MCU) sensitivity, side incidence is the worst direction, with the highest MCU ratio. The largest MCU for the 14 nm FinFET SRAM involves 8 bits. Monte-Carlo simulations are further performed to reveal the characteristics of neutron induced secondary ions and understand the inner mechanisms.

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Solid-to-molecular-orientational-hexatic melting induced by local environment determined defect proliferations Zhanglin Hou(侯章林), Jieli Wang(王杰利), Ying Zeng(曾颖), Zhiyuan Zhao(赵志远), Xing Huang(黄兴), Kun Zhao(赵坤), and Fangfu Ye(叶方富) Chin. Phys. B, 2022, 31 (12):  126401.  DOI: 10.1088/1674-1056/ac8ce1 Abstract ( 338 )   HTML ( 0 )   PDF (5230KB) ( 168 )   Two-dimensional (2D) melting is a fundamental research topic in condensed matter physics, which can also provide guidance on fabricating new functional materials. Nevertheless, our understanding of 2D melting is still far from being complete due to existence of possible complicate transition mechanisms and absence of effective analysis methods. Here, using Monte Carlo simulations, we investigate 2D melting of 60° rhombs which melt from two different surface-fully-coverable crystals, a complex hexagonal crystal (cHX) whose primitive cell contains three rhombs, and a simple rhombic crystal (RB) whose primitive cell contains one rhomb. The melting of both crystals shows a sequence of solid, hexatic in molecular orientation (Hmo), and isotropic phases which obey the Berezinskii-Kosterlitz-Thouless-Halperin-Nelson-Young (BKTHNY) theory. However, local polymorphic configuration (LPC) based analysis reveals different melting mechanisms: the cHX-Hmo transition is driven by the proliferation of point-like defects during which defect-associated LPCs are generated sequentially, whereas the RB-Hmo transition is driven by line defects where defect-associated LPCs are generated simultaneously. These differences result in the observed different solid-Hmo transition points which are φA=0.812 for the cHX-Hmo and φA=0.828 for the RB-Hmo. Our work will shed light on the initial-crystal-dependence of 2D melting behavior.

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Anomalous strain effect in heteroepitaxial SrRuO3 films on (111) SrTiO3 substrates Zhenzhen Wang(王珍珍), Weiheng Qi(戚炜恒), Jiachang Bi(毕佳畅), Xinyan Li(李欣岩), Yu Chen(陈雨), Fang Yang(杨芳), Yanwei Cao(曹彦伟), Lin Gu(谷林), Qinghua Zhang(张庆华), Huanhua Wang(王焕华), Jiandi Zhang(张坚地), Jiandong Guo(郭建东), and Xiaoran Liu(刘笑然) Chin. Phys. B, 2022, 31 (12):  126801.  DOI: 10.1088/1674-1056/ac8725 Abstract ( 416 )   HTML ( 0 )   PDF (1388KB) ( 286 )   We report comprehensive investigations into the structure of high-quality (111)-oriented SrRuO3 films on SrTiO3 substrates to elucidate the effect of (111) heteroepitaxial strain. We found that SrRuO3 film with a thickness of ～ 40 nm is compressively strained in plane on the substrate with full coherency. Nevertheless, the out-of-plane spacing is almost the same as in the bulk, which is at odds with the conventional paradigm. By probing a series of half-order Bragg reflections using synchrotron-based x-ray diffraction combined with analyses of the scanning transmission electron microscopy images, we discovered that the heteroepitaxial strain is accommodated via significant suppression of the degree of c+ octahedral tilting and the formation of three equivalent domain structures on the (111) SrTiO3 substrate. This anomalous effect sheds light on the understanding of an unconventional paradigm of film-substrate coupling for the (111) heteroepitaxial strain.

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Solid-gas interface thermal conductance for the thermal barrier coating with surface roughness: The confinement effect Xue Zhao(赵雪) and Jin-Wu Jiang(江进武) Chin. Phys. B, 2022, 31 (12):  126802.  DOI: 10.1088/1674-1056/ac9041 Abstract ( 374 )   HTML ( 1 )   PDF (1012KB) ( 255 )   The yttria-stabilized zirconia (YSZ) is a famous thermal barrier coating material to protect hot-end components of an engine. As a characteristic feature of the YSZ, the surface roughness shall play an important role in the interface thermal conductance between the YSZ and gas, considering that the gas is typically at an extremely high temperature. We investigate the effect of the surface roughness on the thermal conductance of the YSZ-gas interface with surface roughness described by nanoscale pores on the surface of the YSZ. We reveal two competitive mechanisms related to the microstructure of the pore, i.e., the actual contact area effect and the confinement effect. The increase of the pore depth will enlarge the actual contact area between the YSZ and gas, leading to enhancement of the solid-gas interface thermal conductance. In contrast to the positive actual contact area effect, the geometry-induced confinement effect greatly reduces the interface thermal conductance. These findings shall offer some fundamental understandings for the microscopic mechanisms of the YSZ-gas interface thermal conductance.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Tunable terahertz acoustic-phonon emission from monolayer molybdenum disulfide Cheng-Xiang Zhao(赵承祥), Miao-Miao Zheng(郑苗苗), Yuan Qie(郄媛), and Fang-Wei Han(韩方微) Chin. Phys. B, 2022, 31 (12):  127202.  DOI: 10.1088/1674-1056/ac7f8d Abstract ( 329 )   HTML ( 1 )   PDF (1315KB) ( 48 )   The acoustic-phonon emission from monolayer molybdenum disulfide (ML-MoS2) driven by a direct-current electric field is studied theoretically using the Boltzmann equation method. It is found that the Cerenkov emission of terahertz acoustic-phonons can be generated when a very weak electric field is applied to ML-MoS2. The physical mechanisms of acoustic-phonon emission are analyzed from the perspective of condensed matter physics. The acoustic-phonon emission from ML-MoS2 is also compared with those from graphene and GaAs. The results reveal that the frequencies of acoustic-phonons generated by ML-MoS2 are between the frequencies of those generated from GaAs and graphene. The results of this work suggest that the ML-MoS2 can make up for graphene and GaAs in respect of acoustic-phonon emission and be used in tunable hypersonic devices such as terahertz sound sources.

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High-temperature nodal ring semimetal in two-dimensional honeycomb-kagome Mn2N3 lattice Xin-Ke Liu(刘鑫柯), Xin-Yang Li(李欣阳), Miao-Juan Ren(任妙娟),Pei-Ji Wang(王培吉), and Chang-Wen Zhang(张昌文) Chin. Phys. B, 2022, 31 (12):  127203.  DOI: 10.1088/1674-1056/ac921c Abstract ( 280 )   HTML ( 0 )   PDF (3065KB) ( 85 )   The search for two-dimensional (2D) nodal ring semimetallic materials is a current research hotspot in spintronics, and designing a 2D nodal ring (NR) material with high Curie temperature ($T_{\mathrm{C}})$ and strong robustness to spin-orbit coupling (SOC) is an even greater challenge. Here, based on the first-principles calculations and symmetry analysis, we predict that 2D Mn$_{2}$N$_{3}$ is a nodal ring semimetal (NRSM) with three energy bands near the Fermi energy level consisting of electrons in the same spin channel. An electron-like energy band and two hole-like energy bands near the Fermi plane cross to form two NRs centered at the point $\varGamma $. Symmetry analysis shows that the spin-polarized NR semimetal is robust to SOC due to the conservation of horizontal mirror symmetry. Monte-Carlo simulations further demonstrate that the $T_{\mathrm{C}}$ of the 2D Mn$_{2}$N$_{3}$ reaches 530 K, well above the room temperature. Notably, the 2D Mn$_{2}$N$_{3}$ remains an NRSM on h-BN substrate. Our results not only reveal a general framework for designing 2D NR materials, but also promote further research in the direction of multifunctional quantum devices for spintronics.

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Spin transport properties in ferromagnet/superconductor junctions on topological insulator Hong Li(李红) and Xin-Jian Yang(杨新建) Chin. Phys. B, 2022, 31 (12):  127301.  DOI: 10.1088/1674-1056/ac989e Abstract ( 312 )   HTML ( 0 )   PDF (1032KB) ( 35 )   The spin-dependent Andreev reflection is investigated theoretically by analyzing the electronic transport in a thin-film topological insulator (TI) ferromagnet/superconductor (FM/SC) junction. The tunneling conductance and shot noise are calculated based on the Dirac-Bogoliubov-de Gennes equation and Blonder-Tinkham-Klapwijk theory. It is found that the magnetic gap in ferromagnet can enhance the Andreev retro-reflection but suppress the specular Andreev reflection. The gate potential applied to the electrode on top of superconductor can enhance the two types of reflections. There is a transition between the two types of reflections at which both the tunneling conductance and differential shot noise become zero. These results provide a method to realize and detect experimentally the intra-band specular Andreev reflection in thin film TI-based FM/SC structures.

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Large positive magnetoresistance in photocarrier-doped potassium tantalites Rui-Shu Yang(杨睿姝), Ding-Bang Wang(王定邦), Yang Zhao(赵阳), Shuan-Hu Wang(王拴虎), and Ke-Xin Jin(金克新) Chin. Phys. B, 2022, 31 (12):  127302.  DOI: 10.1088/1674-1056/ac6742 Abstract ( 295 )   HTML ( 1 )   PDF (1442KB) ( 296 )   We report on the high-field magnetotransport of KTaO3 single crystals, which are a promising candidate for study in the extreme quantum limit. By photocarrier doping with 360 nm light, we observe a significant positive, non-saturating, and linear magnetoresistance at low temperatures accompanied by a decreasing Hall coefficient. When cooling down to 10 K, the magnetoresistance value of KTaO3 (100) reaches ～ 433% at a magnetic field of 12 T. Such behavior can be attributed to all the electrons occupying only the lowest Landau level in the extreme quantum limit. Light inhomogeneity may also contribute to large linear magnetoresistance. These results provide insights into novel magnetic devices based on complex materials and add a new family of materials with positive magnetoresistance.

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Manipulation of intrinsic quantum anomalous Hall effect in two-dimensional MoYN2CSCl MXene Yezhu Lv(吕叶竹), Peiji Wang(王培吉), and Changwen Zhang(张昌文) Chin. Phys. B, 2022, 31 (12):  127303.  DOI: 10.1088/1674-1056/ac89d5 Abstract ( 380 )   HTML ( 0 )   PDF (6450KB) ( 83 )   Quantum anomalous Hall effect (QAHE) is an innovative topological spintronic phenomenon with dissipationless chiral edge states and attracts rapidly increasing attention. However, it has only been observed in few materials in experiments. Here, according to the first-principles calculations, we report that the MXene MoYN$_{2}$CSCl shows a topologically nontrivial band gap of 37.3~meV, possessing QAHE with a Chern number of $C = 1$, which is induced by band inversion between $ {\rm d}_{xz}$ and ${\rm d}_{yz}$ orbitals. Also, the topological phase transition for the MoYN$_{2}$CSCl can be realized via strain or by turning the magnetization direction. Remarkably, MoYN$_{2}$CSCl shows the nodal-line semimetal state dependent on the electron correlation $U$. Our findings add an experimentally accessible and tunable member to the QAHE family, which stands a chance of enriching the applications in spintronics.

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Magnetic properties and magnetocaloric effects of Tm1-xErxCuAl (x = 0.25, 0.5, and 0.75) compounds Hao Sun(孙浩), Junfeng Wang(王俊峰), Lu Tian(田路), Jianjian Gong(巩建建), Zhaojun Mo(莫兆军), Jun Shen(沈俊), and Baogen Shen(沈保根) Chin. Phys. B, 2022, 31 (12):  127501.  DOI: 10.1088/1674-1056/ac89d8 Abstract ( 568 )   HTML ( 1 )   PDF (1778KB) ( 191 )   We investigate the structural, magnetic, and magnetocaloric effects (MCE) of Tm$_{1-x}$Er$_{x}$CuAl ($x = 0.25$, 0.5, and 0.75) compounds. The compounds undergo a second-order phase transition originating from the ferromagnetic to paramagnetic transition around 3.2 K, 5 K, and 6 K, respectively. The maximum magnetic entropy changes (${-\Delta S}_{\scriptscriptstyle{\rm M}}^{\rm max}$) of Tm$_{1-x}$Er$_{x}$CuAl ($x = 0.25$, 0.5, and 0.75) are 17.1 J$\cdot$kg$^{-1}\cdot$K$^{-1}$, 18.1 J$\cdot$kg$^{-1}\cdot$K$^{-1}$, and 17.5 J$\cdot$kg$^{-1}\cdot$K$^{-1}$ under the magnetic field in the range of 0-2 T, with the corresponding refrigerant capacity (RC) values of 131 J$\cdot$kg$^{-1}$, 136 J$\cdot$kg$^{-1}$, and 126 J$\cdot$kg$^{-1}$, respectively. The increase of ${-\Delta S}_{\scriptscriptstyle{\rm M}}^{\rm max}$ for Tm$_{0.5}$Er$_{0.5}$CuAl may be relevant to the change of magnetic moment distribution of Er and stress coming from element substitution. This work provides several compounds that can enrich the family of giant MCE materials in the cryogenic region.

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In-plane current-induced magnetization reversal of Pd/CoZr/MgO magnetic multilayers Jing Liu(刘婧), Caiyin You(游才印), Li Ma(马丽), Yun Li(李云), Ling Ma(马凌), and Na Tian(田娜) Chin. Phys. B, 2022, 31 (12):  127502.  DOI: 10.1088/1674-1056/ac891d Abstract ( 370 )   HTML ( 0 )   PDF (746KB) ( 154 )   High critical current density ($> 10^{6}$ A/cm$^{2})$ is one of major obstacles to realize practical applications of the current-driven magnetization reversal devices. In this work, we successfully prepared Pd/CoZr(3.5 nm)/MgO thin films with large perpendicular magnetic anisotropy and demonstrated a way of reducing the critical current density with a low out-of-plane magnetic field in the Pd/CoZr/MgO stack. Under the assistance of an out-of-plane magnetic field, the magnetization can be fully reversed with a current density of about 10$^{4}$ A/cm$^{2}$. The magnetization reversal is attributed to the combined effect of the out-of-plane magnetic field and the current-induced spin-orbital torque. It is found that the current-driven magnetization reversal is highly relevant to the temperature owing to the varied spin-orbital torque, and the current-driven magnetization reversal will be more efficient in low-temperature range, while the magnetic field is helpful for the magnetization reversal in high-temperature range.

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Observation of nonlinearity and heating-induced frequency shifts in cavity magnonics Hot! Wei-Jiang Wu(吴维江), Da Xu(徐达), Jie Qian(钱洁), Jie Li(李杰), Yi-Pu Wang(王逸璞), and Jian-Qiang You(游建强) Chin. Phys. B, 2022, 31 (12):  127503.  DOI: 10.1088/1674-1056/ac9b02 Abstract ( 636 )   HTML ( 3 )   PDF (1892KB) ( 529 )   When there is a certain amount of field inhomogeneity, the biased ferrimagnetic crystal can exhibit the higher-order magnetostatic (HMS) mode in addition to the uniform-precession Kittel mode. In cavity magnonics, we show the nonlinearity and heating-induced frequency shifts of the Kittel mode and HMS mode in a yttrium-iron-garnet (YIG) sphere. When the Kittel mode is driven to generate a certain number of excitations, the temperature of the whole YIG sample rises and the HMS mode can display an induced frequency shift, and vice versa. This cross effect provides a new method to study the magnetization dynamics and paves a way for novel cavity magnonic devices by including the heating effect as an operational degree of freedom.

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Normally-off AlGaN/GaN heterojunction field-effect transistors with in-situ AlN gate insulator Taofei Pu(蒲涛飞), Shuqiang Liu(刘树强), Xiaobo Li(李小波), Ting-Ting Wang(王婷婷), Jiyao Du(都继瑶), Liuan Li(李柳暗), Liang He(何亮), Xinke Liu(刘新科), and Jin-Ping Ao(敖金平) Chin. Phys. B, 2022, 31 (12):  127701.  DOI: 10.1088/1674-1056/ac7a0e Abstract ( 359 )   HTML ( 0 )   PDF (1297KB) ( 91 )   AlGaN/GaN heterojunction field-effect transistors (HFETs) with p-GaN cap layer are developed for normally-off operation, in which an in-situ grown AlN layer is utilized as the gate insulator. Compared with the SiNx gate insulator, the AlN/p-GaN interface presents a more obvious energy band bending and a wider depletion region, which helps to positively shift the threshold voltage. In addition, the relatively large conduction band offset of AlN/p-GaN is beneficial to suppress the gate leakage current and enhance the gate breakdown voltage. Owing to the introduction of AlN layer, normally-off p-GaN capped AlGaN/GaN HFET with a threshold voltage of 4 V and a gate swing of 13 V is realized. Furthermore, the field-effect mobility is approximately 1500 cm2·V-1·s-1 in the 2DEG channel, implying a good device performance.

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Luminescent characteristics of Tm3+/Tb3+/Eu3+ tri-doped Na5Y9F32 single crystals for white emission with high thermal stability Lizhi Fang(方立志), Xiong Zhou(周雄), Zhiwei Zhao(赵志伟), Biao Zheng(郑标), Haiping Xia(夏海平), Jun Wang(王军), Hongwei Song(宋宏伟), and Baojiu Chen(陈宝玖) Chin. Phys. B, 2022, 31 (12):  127802.  DOI: 10.1088/1674-1056/ac6160 Abstract ( 471 )   HTML ( 0 )   PDF (1545KB) ( 47 )   By using an improved Bridgman method, 0.3 mol% Tm$^{3+}/0.6$ mol% Tb$^{3+}/y$ mol% Eu$^{3+}$ ($y = 0$, 0.4, 0.6, 0.8) doped Na$_{5}$Y$_{9}$F$_{32}$ single crystals were prepared. The x-ray diffraction, excitation spectra, emission spectra and fluorescence decay curves were used to explore the crystal structure and optical performance of the obtained samples. When excited by 362 nm light, the cool white emission was realized by Na$_{5}$Y$_{9}$F$_{32}$ single crystal triply-doped with 0.3 mol% Tm$^{3+}/0.6$ mol% Tb$^{3+}/0.8$ mol% Eu$^{3+}$, in which the Commission Internationale de l'Eclairage (CIE) chromaticity coordinate was (0.2995, 0.3298) and the correlated color temperature (CCT) was 6586 K. The integrated normalized emission intensity of the tri-doped single crystal at 448 K could keep 62% of that at 298 K. The internal quantum yield (QY) was calculated to be $\sim 15.16$% by integrating spheres. These results suggested that the single crystals tri-doped with Tm$^{3+}$, Tb$^{3+}$ and Eu$^{3+}$ ions have a promising potential application for white light-emitting diodes (w-LEDs).

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Effect of oxygen on regulation of properties of moderately boron-doped diamond films Dong-Yang Liu(刘东阳), Li-Cai Hao(郝礼才), Wei-Kang Zhao(赵伟康), Zi-Ang Chen(陈子昂), Kun Tang(汤琨), Shun-Ming Zhu(朱顺明), Jian-Dong Ye(叶建东), Rong Zhang(张荣), You-Dou Zheng(郑有炓), and Shu-Lin Gu(顾书林) Chin. Phys. B, 2022, 31 (12):  128104.  DOI: 10.1088/1674-1056/ac8e96 Abstract ( 326 )   HTML ( 0 )   PDF (1093KB) ( 179 )   Regulation of oxygen on properties of moderately boron-doped diamond films is fully investigated. Results show that, with adding a small amount of oxygen (oxygen-to-carbon ratio < 5.0%), the crystal quality of diamond is improved, and a suppression effect of residual nitrogen is observed. With increasing ratio of O/C from 2.5% to 20.0%, the hole concentration is firstly increased then reduced. This change of hole concentration is also explained. Moreover, the results of Hall effect measurement with temperatures from 300 K to 825 K show that, with adding a small amount of oxygen, boron and oxygen complex structures (especially B3O and B4O) are formed and exhibit as shallow donor in diamond, which results in increase of donor concentration. With further increase of ratio of O/C, the inhibitory behaviors of oxygen on boron leads to decrease of acceptor concentration (the optical emission spectroscopy has shown that it is decreased with ratio of O/C more than 10.0%). This work demonstrates that oxygen-doping induced increasement of the crystalline and surface quality could be restored by the co-doping with oxygen. The technique could achieve boron-doped diamond films with both high quality and acceptable hole concentration, which is applicable to electronic level of usage.

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Degradation mechanisms for polycrystalline silicon thin-film transistors with a grain boundary in the channel under negative gate bias stress Dongli Zhang(张冬利), Mingxiang Wang(王明湘), and Huaisheng Wang(王槐生) Chin. Phys. B, 2022, 31 (12):  128105.  DOI: 10.1088/1674-1056/ac9823 Abstract ( 334 )   HTML ( 0 )   PDF (879KB) ( 222 )   The negative gate bias stress (NBS) reliability of n-type polycrystalline silicon (poly-Si) thin-film transistors (TFTs) with a distinct defective grain boundary (GB) in the channel is investigated. Results show that conventional NBS degradation with negative shift of the transfer curves is absent. The on-state current is decreased, but the subthreshold characteristics are not affected. The gate bias dependence of the drain leakage current at Vds of 5.0 V is suppressed, whereas the drain leakage current at Vds of 0.1 V exhibits obvious gate bias dependence. As confirmed via TCAD simulation, the corresponding mechanisms are proposed to be trap state generation in the GB region, positive-charge local formation in the gate oxide near the source and drain, and trap state introduction in the gate oxide.

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Origin, characteristics, and suppression of residual nitrogen in MPCVD diamond growth reactor Yan Teng(滕妍), Dong-Yang Liu(刘东阳), Kun Tang(汤琨), Wei-Kang Zhao(赵伟康), Zi-Ang Chen(陈子昂), Ying-Meng Huang(黄颖蒙), Jing-Jing Duan(段晶晶), Yue Bian(卞岳), Jian-Dong Ye(叶建东), Shun-Ming Zhu(朱顺明), Rong Zhang(张荣), You-Dou Zheng(郑有炓), and Shu-Lin Gu(顾书林) Chin. Phys. B, 2022, 31 (12):  128106.  DOI: 10.1088/1674-1056/ac7552 Abstract ( 426 )   HTML ( 3 )   PDF (1603KB) ( 182 )   Unintentional nitrogen incorporation has been observed in a set of microwave plasma chemical vapor deposition (MPCVD)-grown samples. No abnormality has been detected on the apparatus especially the base pressure and feeding gas purity. By a comprehensive investigation including the analysis of the plasma composition, we found that a minor leakage of the system could be significantly magnified by the thermal effect, resulting in a considerable residual nitrogen in the diamond material. Moreover, the doping mechanism of leaked air is different to pure nitrogen doping. The dosage of several ppm of pure nitrogen can lead to efficient nitrogen incorporation in diamond, while at least thousands ppm of leaked air is required for detecting obvious residual nitrogen. The difference of the dosage has been ascribed to the suppression effect of oxygen that consumes nitrogen. As the unintentional impurity is basically detrimental to the controllable fabrication of diamond for electronic application, we have provided an effective way to suppress the residual nitrogen in a slightly leaked system by modifying the susceptor geometry. This study indicates that even if a normal base pressure can be reached, the nitrogen residing in the chamber can be "activated" by the thermal effect and thus be incorporated in diamond material grown by a MPCVD reactor.

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Bottom-up design and assembly with superatomic building blocks Hot! Famin Yu(于法民), Zhonghua Liu(刘中华), Jiarui Li(李佳芮), Wanrong Huang(黄婉蓉), Xinrui Yang(杨欣瑞), and Zhigang Wang(王志刚) Chin. Phys. B, 2022, 31 (12):  128107.  DOI: 10.1088/1674-1056/ac9e97 Abstract ( 645 )   HTML ( 8 )   PDF (1170KB) ( 480 )   Constructing specific structures from the bottom up with artificial units is an important interdisciplinary topic involving physics, chemistry, materials, and so on. In this work, we theoretically demonstrated the feasibility of using superatoms as building blocks to assemble a complex at atomic-level precision. By using a series of actinide-based endohedral metallofullerene (EMF) superatoms that can form one, two, three and four chemical bonds, a planar complex with intra- and inter-molecular interactions was assembled on the Au(111) surface. This complex is composed of two parts, containing ten and eight superatoms, respectively. The electronic structure analysis shows that the electron density inside each part is connected and the closed-shell electronic arrangement system is designed. There is also an obvious van der Waals boundary by physical adsorption between the two parts, and a stable complex is formed. Since this complex is realized by the first-principles calculations of quantum mechanics, our results help not only achieve atomic-level precision construction with artificial superatomic units but also maintain atomic-level functional properties.

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Impact of microsecond-pulsed plasma-activated water on papaya seed germination and seedling growth Deng-Ke Xi(席登科), Xian-Hui Zhang(张先徽), Si-Ze Yang(杨思泽), Seong Shan Yap(叶尚姗), Kenji Ishikawa(石川健治), Masura Hori (堀勝), and Seong Ling Yap(叶尚凌) Chin. Phys. B, 2022, 31 (12):  128201.  DOI: 10.1088/1674-1056/ac904e Abstract ( 350 )   HTML ( 1 )   PDF (2321KB) ( 273 )   The seed of Carica papaya consists of a hard shell-like testa with inhibitors in vivo causing slow, erratic and asynchronous germination. In this work, plasma-activated water prepared by microsecond-pulsed plasma jets (μPAW) was applied to treat papaya seeds. The μPAW after plasma activation of 30 min was about 40 ℃. The reactive species such as NO2, NO3, and H2O2 in the μPAW activated from deionized water were measured and correlated to the seed germination rate and the seedling growth performance. The μPAW-treated papaya seed achieved a higher germination rate of 90%, which is 26% higher than the control group using deionized water. Comparing the results with a hot water (40 ℃) reference group showed that the reactive species in μPAW played primary roles in germination improvement, with little effect caused by the heat shock. The μPAW also sterilized the treated seeds, reducing the germination stress. The morphological change in the seeds was observed by SEM, showing an effect of physical etching after treatment promoting seed imbibition. The biochemical mechanism of the seed germination was deduced with reference to the evolution of surface chemistry, functional groups, and ABA content. The accelerated seed metabolism observed was corresponded to the chemical modification pathway. Besides, early seedlings developed from treated seeds were observed to be healthy, grow more leaves, and have better root structures. The content of MDA in the treated papaya seedlings decreased along with increased SOD and higher ion concentration. The μPAW that can be prepared at atmospheric pressure for bulk production offers a low-risk and cost-effective seed priming technology that may significantly increase the production of agricultural crops.

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Forward-wave enhanced radiation in the terahertz electron cyclotron maser Zi-Chao Gao(高子超), Chao-Hai Du(杜朝海), Fan-Hong Li(李繁弘), Zi-Wen Zhang(张子文), Si-Qi Li(李思琦), and Pu-Kun Liu(刘濮鲲) Chin. Phys. B, 2022, 31 (12):  128401.  DOI: 10.1088/1674-1056/ac90b4 Abstract ( 284 )   HTML ( 2 )   PDF (1440KB) ( 194 )   Based on the principle of electron cyclotron maser (ECM), gyrotrons are among the most promising devices to generate powerful coherent terahertz (THz) radiation and play a vital role in numerous advanced THz applications. Unfortunately, THz ECM systems using a conventional high-Q cavity were theoretically and experimentally demonstrated to suffer from strong ohmic losses, and, accordingly, the wave output efficiency was significantly reduced. A scheme to alleviate such a challenging problem is systematically investigated in this paper. The traveling-wave operation concept is employed in a 1-THz third harmonic gyrotron oscillator, which strengthens electron-wave interaction efficiency and reduces the ohmic dissipation, simultaneously. A lossy belt is added in the interaction circuit to stably constitute the traveling-wave interaction, and a down-tapered magnetic field is employed to further amplify the forward-wave (FW) component. The results demonstrate that the proportion of ohmic losses is nearly halved, and output efficiency is nearly doubled, which is promising for further advancement of high-power continuous-wave operation of the ECM-based devices.

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An insulated-gate bipolar transistor model based on the finite-volume charge method Manhong Zhang(张满红) and Wanchen Wu(武万琛) Chin. Phys. B, 2022, 31 (12):  128501.  DOI: 10.1088/1674-1056/ac8723 Abstract ( 487 )   HTML ( 0 )   PDF (953KB) ( 63 )   A finite-volume charge method has been proposed to simulate PIN diodes and insulated-gate bipolar transistor (IGBT) devices using SPICE simulators by extending the lumped-charge method. The new method assumes local quasi-neutrality in the undepleted N- base region and uses the total collector current, the nodal hole density and voltage as the basic quantities. In SPICE implementation, it makes clear and accurate definitions of three kinds of nodes — the carrier density nodes, the voltage nodes and the current generator nodes — in the undepleted N- base region. It uses central finite difference to approximate electron and hole current generators and sets up the current continuity equation in a control volume for every carrier density node in the undepleted N- base region. It is easy to increase the number of nodes to describe the fast spatially varying carrier density in transient processes. We use this method to simulate IGBT devices in SPICE simulators and get a good agreement with technology computer-aided design simulations.

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High-sensitive phototransistor based on vertical HfSe2/MoS2 heterostructure with broad-spectral response Wen Deng(邓文), Li-Sheng Wang(汪礼胜), Jia-Ning Liu(刘嘉宁), Tao Xiang(相韬), and Feng-Xiang Chen(陈凤翔) Chin. Phys. B, 2022, 31 (12):  128502.  DOI: 10.1088/1674-1056/ac6dc1 Abstract ( 309 )   HTML ( 1 )   PDF (2564KB) ( 81 )   Van der Waals heterostructures based on the two-dimensional (2D) semiconductor materials have attracted increasing attention due to their attractive properties. In this work, we demonstrate a high-sensitive back-gated phototransistor based on the vertical HfSe2/MoS2 heterostructure with a broad-spectral response from near-ultraviolet to near-infrared and an efficient gate tunability for photoresponse. Under bias, the phototransistor exhibits high responsivity of up to 1.42×103 A/W, and ultrahigh specific detectivity of up to 1.39×1015 cm·Hz1/2·W-1. Moreover, it can also operate under zero bias with remarkable responsivity of 10.2 A/W, relatively high specific detectivity of 1.43×1014 cm·Hz1/2·W-1, ultralow dark current of 1.22 fA, and high on/off ratio of above 105. These results should be attributed to the fact that the vertical HfSe2/MoS2 heterostructure not only improves the broadband photoresponse of the phototransistor but also greatly enhances its sensitivity. Therefore, the heterostructure provides a promising candidate for next generation high performance phototransistors.

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Interface effect on superlattice quality and optical properties of InAs/GaSb type-II superlattices grown by molecular beam epitaxy Zhaojun Liu(刘昭君), Lian-Qing Zhu(祝连庆), Xian-Tong Zheng(郑显通), Yuan Liu(柳渊), Li-Dan Lu(鹿利单), and Dong-Liang Zhang(张东亮) Chin. Phys. B, 2022, 31 (12):  128503.  DOI: 10.1088/1674-1056/ac8729 Abstract ( 362 )   HTML ( 1 )   PDF (1671KB) ( 208 )   We systematically investigate the influence of InSb interface (IF) engineering on the crystal quality and optical properties of strain-balanced InAs/GaSb type-II superlattices (T2SLs). The type-II superlattice structure is 120 periods InAs (8 ML)/GaSb (6 ML) with different thicknesses of InSb interface grown by molecular beam epitaxy (MBE). The high-resolution x-ray diffraction (XRD) curves display sharp satellite peaks, and the narrow full width at half maximum (FWHM) of the 0th is only 30-39 arcsec. From high-resolution cross-sectional transmission electron microscopy (HRTEM) characterization, the InSb heterointerfaces and the clear spatial separation between the InAs and GaSb layers can be more intuitively distinguished. As the InSb interface thickness increases, the compressive strain increases, and the surface "bright spots" appear to be more apparent from the atomic force microscopy (AFM) results. Also, photoluminescence (PL) measurements verify that, with the increase in the strain, the bandgap of the superlattice narrows. By optimizing the InSb interface, a high-quality crystal with a well-defined surface and interface is obtained with a PL wavelength of 4.78 μ, which can be used for mid-wave infrared (MWIR) detection.

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Temperature dependence of spin pumping in YIG/NiOx/W multilayer Lijun Ni(倪丽君), Wenqiang Wang(王文强), Lichuan Jin(金立川), Jiandong Ye(叶建东), Hehe Gong(巩贺贺), Xiang Zhan(战翔), Zhendong Chen(陈振东), Longlong Zhang(张龙龙), Xingze Dai(代兴泽), Yao Li(黎遥), Rong Zhang(张荣), Yi Yang(杨燚), Huaiwu Zhang(张怀武), Ronghua Liu(刘荣华), Lina Chen(陈丽娜), and Yongbing Xu(徐永兵) Chin. Phys. B, 2022, 31 (12):  128504.  DOI: 10.1088/1674-1056/ac6333 Abstract ( 329 )   HTML ( 1 )   PDF (1312KB) ( 149 )   We report the temperature dependence of the spin pumping effect for Y3Fe5O12 (YIG, 0.9 μm)/NiO (tNiO)/W (6 nm) (tNiO = 0 nm, 1 nm, 2 nm, and 10 nm) heterostructures. All samples exhibit a strong temperature-dependent inverse spin Hall effect (ISHE) signal Ic and sensitivity to the NiO layer thickness. We observe a dramatic decrease of Ic with inserting thin NiO layer between YIG and W layers indicating that the inserting of NiO layer significantly suppresses the spin transport from YIG to W. In contrast to the noticeable enhancement in YIG/NiO (tNiO ≈ 1-2 nm)/Pt, the suppression of spin transport may be closely related to the specific interface-dependent spin scattering, spin memory loss, and spin conductance at the NiO/W interface. Besides, the Ic of YIG/NiO/W exhibits a maximum near the TN of the AF NiO layer because the spins are transported dominantly by incoherent thermal magnons.

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Parkinsonian oscillations and their suppression by closed-loop deep brain stimulation based on fuzzy concept Xi-Le Wei(魏熙乐), Yu-Lin Bai(白玉林), Jiang Wang(王江), Si-Yuan Chang(常思远), and Chen Liu(刘晨) Chin. Phys. B, 2022, 31 (12):  128701.  DOI: 10.1088/1674-1056/ac8cd8 Abstract ( 270 )   HTML ( 0 )   PDF (2702KB) ( 158 )   This paper provides an adaptive closed-loop strategy for suppressing the pathological oscillations of the basal ganglia based on a variable universe fuzzy algorithm. The pathological basal ganglia oscillations in the theta (4-9 Hz) and beta (12-35 Hz) frequency bands have been demonstrated to be associated with the tremor and rigidity/bradykinesia symptoms in Parkinson's disease (PD). Although the clinical application of open-loop deep brain stimulation (DBS) is effective, the stimulation waveform with the fixed parameters cannot be self-adjusted as the disease progresses, and thus the stimulation effects go poor. To deal with this difficult problem, a variable universe fuzzy closed-loop strategy is proposed to modulate different PD states. We establish a cortico-basal ganglia-thalamocortical network model to simulate pathological oscillations and test the control effect. The results suggest that the proposed closed-loop control strategy can accommodate the variation of brain states and symptoms, which may become an alternative method to administrate the symptoms in PD.

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Low-voltage soft robots based on carbon nanotube/polymer electrothermal composites Qi Wang(王琪), Ying-Qiong Yong(雍颖琼), and Zhi-Ming Bai(白智明) Chin. Phys. B, 2022, 31 (12):  128801.  DOI: 10.1088/1674-1056/ac6dbe Abstract ( 364 )   HTML ( 2 )   PDF (1990KB) ( 81 )   Nowadays, soft robots have become a research hot spot due to high degree of freedom, adaptability to the environment and safer interaction with humans. The carbon nanotube (CNT)/polydimethylsiloxane (PDMS) electrothermal composites have attracted wide attention in the field of flexible actuations due to large deformation at low voltages. Here, the preparation process of CNT/PDMS composites was designed and optimized, and electrothermal actuators (ETAs) were fabricated by cutting the CNT/PDMS composite films into a "U" shape and coating conductive adhesive. The deformation performance of the ETAs with different thicknesses at different voltages was studied. At a low voltage of about 7 V, the ETA has a deformation rate of up to 93%. Finally, two kinds of electrothermal soft robots (ETSRs) with four-legged and three-legged structures were fabricated, and their inchworm-like motion characteristics were studied. The ETSR2 has the best motion performance due to the moderate thickness and three-legged electrode structure.

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Nano Ag-enhanced photoelectric conversion efficiency in all-inorganic, hole-transporting-layer-free CsPbIBr2 perovskite solar cells Youming Huang(黄友铭), Yizhi Wu(吴以治), Xiaoliang Xu(许小亮), Feifei Qin(秦飞飞), Shihan Zhang(张诗涵), Jiakai An(安嘉凯), Huijie Wang(王会杰), and Ling Liu(刘玲) Chin. Phys. B, 2022, 31 (12):  128802.  DOI: 10.1088/1674-1056/ac89e8 Abstract ( 455 )   HTML ( 0 )   PDF (4167KB) ( 163 )   All-inorganic, hole-transporting-layer-free CsPbIBr2 perovskite solar cells have great potential for development, but their device performance needs to be further improved. Recently, metal nanostructures have been successfully applied in the field of solar cells to improve their performance. Nano Ag-enhanced power conversion efficiency (PCE) in one CsPbIBr2 perovskite solar cell utilizing localized surface plasmons of Ag nanoparticles (NPs) on the surface has been researched experimentally and by simulation in this paper. The localized surface plasmon resonance of Ag NPs has a near-field enhancement effect, which is expected to improve the light absorption of CsPbIBr2 perovskite photovoltaic devices. In addition, Ag NPs have a forward-scattering effect on the incident light, which can also improve the performance of CsPbIBr2-based perovskite photovoltaic devices. By directly assembling Ag NPs (with a size of about 150 nm) on the surface of fluorine-doped tin oxide it is found when the particle surface coverage is 10%, the CsPbIBr2 perovskite photovoltaic device achieves a best PCE of 2.7%, which is 9.76% higher than that of the control group. Without changing any existing structure in the ready-made solar cell, this facile and efficient method has huge applications. To the best of our knowledge, this paper is the first report on nano Ag-enhanced photoelectric conversion efficiency in this kind of CsPbIBr2 perovskite solar cell.

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Fault-tolerant finite-time dynamical consensus of double-integrator multi-agent systems with partial agents subject to synchronous self-sensing function failure Zhi-Hai Wu(吴治海) and Lin-Bo Xie(谢林柏) Chin. Phys. B, 2022, 31 (12):  128902.  DOI: 10.1088/1674-1056/ac8347 Abstract ( 339 )   HTML ( 0 )   PDF (858KB) ( 79 )   This paper investigates fault-tolerant finite-time dynamical consensus problems of double-integrator multi-agent systems (MASs) with partial agents subject to synchronous self-sensing function failure (SSFF). A strategy of recovering the connectivity of network topology among normal agents based on multi-hop communication and a fault-tolerant finite-time dynamical consensus protocol with time-varying gains are proposed to resist synchronous SSFF. It is proved that double-integrator MASs with partial agents subject to synchronous SSFF using the proposed strategy of network topology connectivity recovery and fault-tolerant finite-time dynamical consensus protocol with the proper time-varying gains can achieve finite-time dynamical consensus. Numerical simulations are given to illustrate the effectiveness of the theoretical results.