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Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For selected: Download citations EndNote Ris BibTeX Toggle thumbnails Select Superconductivity in an intermetallic oxide Hf3Pt4Ge2O Chengchao Xu(徐程超), Hong Wang(王鸿), Huanfang Tian(田焕芳), Youguo Shi(石友国), Zi-An Li(李子安), Ruijuan Xiao(肖睿娟), Honglong Shi(施洪龙), Huaixin Yang(杨槐馨), and Jianqi Li(李建奇) Chin. Phys. B, 2021, 30 (7): 077403.   DOI: 10.1088/1674-1056/abfb53 Abstract （770）   HTML （1）    PDF （3238KB）（526）       Knowledge map    Discovery of a new superconductor with distinct crystal structure and chemistry often provides great opportunity for further expanding superconductor material base, and also leads to better understanding of superconductivity mechanisms. Here, we report the discovery of superconductivity in a new intermetallic oxide Hf3Pt4Ge2O synthesized through a solid-state reaction. The Hf3Pt4Ge2O crystallizes in a cubic structure (space group Fm-3m) with a lattice constant of a = 1.241 nm, whose stoichiometry and atomic structure are determined by electron microscopy and x-ray diffraction techniques. The superconductivity at 4.1 K and type-Ⅱ superconducting nature are evidenced by the electrical resistivity, magnetic susceptibility, and specific heat measurements. The intermetallic oxide Hf3Pt4Ge2O system demonstrates an intriguing structural feature that foreign oxygen atoms can be accommodated in the interstitial sites of the ternary intermetallic framework. We also successfully synthesized a series of Hf3Pt4Ge2O1+δ (-0.25 ≤ δ ≤ 0.5), and found the δ-dependent superconducting transition temperature Tc. The atomic structure and the electronic structure are also substantiated by first-principles calculations. Our results present an entirely new family of superconductors with distinct structural and chemical characteristics, and could attract research interest in further finding new superconductors and exploring novel physics pertaining to the 5d-electron in these intermetallic compound systems. Select Magnetism and giant magnetocaloric effect in rare-earth-based compounds R3BWO9 (R = Gd, Dy, Ho) Lu-Ling Li(李炉领), Xiao-Yu Yue(岳小宇), Wen-Jing Zhang(张文静), Hu Bao(鲍虎), Dan-Dan Wu(吴丹丹), Hui Liang(梁慧), Yi-Yan Wang(王义炎), Yan Sun(孙燕), Qiu-Ju Li(李秋菊), and Xue-Feng Sun(孙学峰) Chin. Phys. B, 2021, 30 (7): 077501.   DOI: 10.1088/1674-1056/abf916 Abstract （761）   HTML （2）    PDF （2664KB）（333）       Knowledge map    The magnetism and magnetocaloric effect (MCE) of rare-earth-based tungstate compounds $R_{3}$BWO$_{9 }$ ($R = {\rm Gd}$, Dy, Ho) have been studied by magnetic susceptibility, isothermal magnetization, and specific heat measurements. No obvious long-range magnetic ordering can be found down to 2 K. The Curie-Weiss fitting and magnetic susceptibilities under different applied fields reveal the existence of weak short-range antiferromagnetic couplings at low temperature in these systems. The calculations of isothermal magnetization exhibit a giant MCE with the maximum changes of magnetic entropy being 54.80 J/kg$\cdot$K at 2 K for Gd$_{3}$BWO$_{9}$, 28.5 J/kg$\cdot$K at 6 K for Dy$_{3}$BWO$_{9}$, and 29.76 J/kg$\cdot$K at 4 K for Ho$_{3}$BWO$_{9}$, respectively, under a field change of 0-7 T. Especially for Gd$_{3}$BWO$_{9}$, the maximum value of magnetic entropy change ($-\Delta S_{M}^{\max}$) and adiabatic temperature change ($ - \Delta T_{\rm ad}^{\max}$) are 36.75 J/kg$\cdot$K and 5.56 K for a low field change of 0-3 T, indicating a promising application for low temperature magnetic refrigeration. Select Electronic structures and topological properties of TeSe2 monolayers Zhengyang Wan(万正阳), Hao Huan(郇昊), Hairui Bao(鲍海瑞), Xiaojuan Liu(刘晓娟), and Zhongqin Yang(杨中芹) Chin. Phys. B, 2021, 30 (11): 117304.   DOI: 10.1088/1674-1056/ac2489 Abstract （742）   HTML （4）    PDF （2793KB）（466）       Knowledge map    The successfully experimental fabrication of two-dimensional Te monolayer films [Phys. Rev. Lett. 119 106101 (2017)] has promoted the researches on the group-VI monolayer materials. In this work, the electronic structures and topological properties of a group-VI binary compound of TeSe2 monolayers are studied based on the density functional theory and Wannier function method. Three types of structures, namely, α-TeSe2, β-TeSe2, and γ-TeSe2, are proposed for the TeSe2 monolayer among which the α-TeSe2 is found being the most stable. All the three structures are semiconductors with indirect band gaps. Very interestingly, the γ-TeSe2 monolayer becomes a quantum spin Hall (QSH) insulator with a global nontrivial energy gap of 0.14 eV when a 3.5% compressive strain is applied. The opening of the global band gap is understood by the competition between the decrease of the local band dispersion and the weakening of the interactions between the Se px, py orbitals and Te px, py orbitals during the process. Our work realizes topological states in the group-VI monolayers and promotes the potential applications of the materials in spintronics and quantum computations. Select Emergent O(4) symmetry at the phase transition from plaquette-singlet to antiferromagnetic order in quasi-two-dimensional quantum magnets Guangyu Sun(孙光宇), Nvsen Ma(马女森), Bowen Zhao(赵博文), Anders W. Sandvik, and Zi Yang Meng(孟子杨) Chin. Phys. B, 2021, 30 (6): 067505.   DOI: 10.1088/1674-1056/abf3b8 Abstract （729）   HTML （1）    PDF （4649KB）（374）       Knowledge map    Recent experiments[Guo et al., Phys. Rev. Lett. 124 206602 (2020)] on thermodynamic properties of the frustrated layered quantum magnet SrCu2(BO3)2—the Shastry-Sutherland material—have provided strong evidence for a low-temperature phase transition between plaquette-singlet and antiferromagnetic order as a function of pressure. Further motivated by the recently discovered unusual first-order quantum phase transition with an apparent emergent O(4) symmetry of the antiferromagnetic and plaquette-singlet order parameters in a two-dimensional "checkerboard J-Q" quantum spin model[Zhao et al., Nat. Phys. 15 678 (2019)], we here study the same model in the presence of weak inter-layer couplings. Our focus is on the evolution of the emergent symmetry as the system crosses over from two to three dimensions and the phase transition extends from strictly zero temperature in two dimensions up to finite temperature as expected in SrCu2(BO3)2. Using quantum Monte Carlo simulations, we map out the phase boundaries of the plaquette-singlet and antiferromagnetic phases, with particular focus on the triple point where these two ordered phases meet the paramagnetic phase for given strength of the inter-layer coupling. All transitions are first-order in the neighborhood of the triple point. We show that the emergent O(4) symmetry of the coexistence state breaks down clearly when the interlayer coupling becomes sufficiently large, but for a weak coupling, of the magnitude expected experimentally, the enlarged symmetry can still be observed at the triple point up to significant length scales. Thus, it is likely that the plaquette-singlet to antiferromagnetic transition in SrCu2(BO3)2 exhibits remnants of emergent O(4) symmetry, which should be observable due to additional weakly gapped Goldstone modes. Select Effective model for rare-earth Kitaev materials and its classical Monte Carlo simulation Mengjie Sun(孙梦杰), Huihang Lin(林慧航), Zheng Zhang(张政), Yanzhen Cai(蔡焱桢), Wei Ren(任玮), Jing Kang(康靖), Jianting Ji(籍建葶), Feng Jin(金峰), Xiaoqun Wang(王孝群), Rong Yu(俞榕), Qingming Zhang(张清明), and Zhengxin Liu(刘正鑫) Chin. Phys. B, 2021, 30 (8): 087503.   DOI: 10.1088/1674-1056/ac0a5d Abstract （620）   HTML （0）    PDF （2226KB）（362）       Knowledge map    Recently, the family of rare-earth chalcohalides were proposed as candidate compounds to realize the Kitaev spin liquid (KSL) [Chin. Phys. Lett. 38 047502 (2021)]. In the present work, we firstly propose an effective spin Hamiltonian consistent with the symmetry group of the crystal structure. Then we apply classical Monte Carlo simulations to preliminarily study the model and establish a phase diagram. When approaching to the low temperature limit, several magnetic long range orders are observed, including the stripe, the zigzag, the antiferromagnetic (AFM), the ferromagnetic (FM), the incommensurate spiral (IS), the multi-Q, and the 120° ones. We further calculate the thermodynamic properties of the system, such as the temperature dependence of the magnetic susceptibility and the heat capacity. The ordering transition temperatures reflected in the two quantities agree with each other. For most interaction regions, the system is magnetically more susceptible in the ab-plane than in the c-direction. The stripe phase is special, where the susceptibility is fairly isotropic in the whole temperature region. These features provide useful information to understand the magnetic properties of related materials. Select Strain-dependent resistance and giant gauge factor in monolayer WSe2 Mao-Sen Qin(秦茂森), Xing-Guo Ye(叶兴国), Peng-Fei Zhu(朱鹏飞), Wen-Zheng Xu(徐文正), Jing Liang(梁晶), Kaihui Liu(刘开辉), and Zhi-Min Liao(廖志敏) Chin. Phys. B, 2021, 30 (9): 097203.   DOI: 10.1088/1674-1056/ac11d2 Abstract （589）   HTML （3）    PDF （949KB）（333）       Knowledge map    We report the strong dependence of resistance on uniaxial strain in monolayer WSe2 at various temperatures, where the gauge factor can reach as large as 2400. The observation of strain-dependent resistance and giant gauge factor is attributed to the emergence of nonzero Berry curvature dipole. Upon increasing strain, Berry curvature dipole can generate net orbital magnetization, which would introduce additional magnetic scattering, decreasing the mobility and thus conductivity. Our work demonstrates the strain engineering of Berry curvature and thus the transport properties, making monolayer WSe2 potential for application in the highly sensitive strain sensors and high-performance flexible electronics. Select Giant Rashba-like spin-orbit splitting with distinct spin texture in two-dimensional heterostructures Jianbao Zhu(朱健保), Wei Qin(秦维), and Wenguang Zhu(朱文光) Chin. Phys. B, 2021, 30 (8): 087307.   DOI: 10.1088/1674-1056/ac0784 Abstract （586）   HTML （1）    PDF （2029KB）（237）       Knowledge map    Based on first-principles density functional theory calculation, we discover a novel form of spin-orbit (SO) splitting in two-dimensional (2D) heterostructures composed of a single Bi(111) bilayer stacking with a 2D semiconducting In2Se2 or a 2D ferroelectric α-In2Se3 layer. Such SO splitting has a Rashba-like but distinct spin texture in the valence band around the maximum, where the chirality of the spin texture reverses within the upper spin-split branch, in contrast to the conventional Rashba systems where the upper branch and lower branch have opposite chirality solely in the region below the band crossing point. The ferroelectric nature of α-In2Se3 further enables the tuning of the spin texture upon the reversal of the electric polarization with the application of an external electric field. Detailed analysis based on a tight-binding model reveals that such SO splitting texture results from the interplay of complex orbital characters and substrate interaction. This finding enriches the diversity of SO splitting systems and is also expected to promise for spintronic applications. Select Abnormal phenomenon of source-drain current of AlGaN/GaN heterostructure device under UV/visible light irradiation Yue-Bo Liu(柳月波), Jun-Yu Shen(沈俊宇), Jie-Ying Xing(邢洁莹), Wan-Qing Yao(姚婉青), Hong-Hui Liu(刘红辉), Ya-Qiong Dai(戴雅琼), Long-Kun Yang(杨隆坤), Feng-Ge Wang(王风格), Yuan Ren(任远), Min-Jie Zhang(张敏杰), Zhi-Sheng Wu(吴志盛), Yang Liu(刘扬), and Bai-Jun Zhang(张佰君) Chin. Phys. B, 2021, 30 (11): 117302.   DOI: 10.1088/1674-1056/abfa07 Abstract （582）   HTML （0）    PDF （1845KB）（27）       Knowledge map    We report an abnormal phenomenon that the source-drain current (ID) of AlGaN/GaN heterostructure devices decreases under visible light irradiation. When the incident light wavelength is 390 nm, the photon energy is less than the band gaps of GaN and AlGaN whereas it can causes an increase of ID. Based on the UV light irradiation, a decrease of ID can still be observed when turning on the visible light. We speculate that this abnormal phenomenon is related to the surface barrier height, the unionized donor-like surface states below the surface Fermi level and the ionized donor-like surface states above the surface Fermi level. For visible light, its photon energy is less than the surface barrier height of the AlGaN layer. The electrons bound in the donor-like surface states below the Fermi level are excited and trapped by the ionized donor-like surface states between the Fermi level and the conduction band of AlGaN. The electrons trapped in ionized donor-like surface states show a long relaxation time, and the newly ionized donor-like surface states below the surface Fermi level are filled with electrons from the two-dimensional electron gas (2DEG) channel at AlGaN/GaN interface, which causes the decrease of ID. For the UV light, when its photon energy is larger than the surface barrier height of the AlGaN layer, electrons in the donor-like surface states below the Fermi level are excited to the conduction band and then drift into the 2DEG channel quickly, which cause the increase of ID. Select Fabrication of sulfur-doped cove-edged graphene nanoribbons on Au(111) Huan Yang(杨欢), Yixuan Gao(高艺璇), Wenhui Niu(牛雯慧), Xiao Chang(常霄), Li Huang(黄立), Junzhi Liu(刘俊治), Yiyong Mai(麦亦勇), Xinliang Feng(冯新亮), Shixuan Du(杜世萱), and Hong-Jun Gao(高鸿钧) Chin. Phys. B, 2021, 30 (7): 077306.   DOI: 10.1088/1674-1056/abfbd0 Abstract （566）   HTML （4）    PDF （1596KB）（229）       Knowledge map    The on-surface synthesis from predesigned organic precursors can yield graphene nanoribbons (GNRs) with atomically precise widths, edge terminations and dopants, which facilitate the tunning of their electronic structures. Here, we report the synthesis of novel sulfur-doped cove-edged GNRs (S-CGNRs) on Au(111) from a specifically designed precursor containing thiophene rings. Scanning tunneling microscopy and non-contact atomic force microscopy measurements elucidate the formation of S-CGNRs through subsequent polymerization and cyclodehydrogenation, which further result in crosslinked branched structures. Scanning tunneling spectroscopy results reveal the conduction band minimum of the S-CGNR locates at 1.2 eV. First-principles calculations show that the S-CGNR possesses an energy bandgap of 1.17 eV, which is evidently smaller than that of an undoped cove-edged GNR (1.7 eV), suggesting effective tuning of the bandgap by introducing sulfur atoms. Further increasing the coverage of precursors close to a monolayer results in the formation of linear-shaped S-CGNRs. The fabrication of S-CGNRs provides one more candidate in the GNR toolbox and promotes the future applications of heteroatom-doped graphene nanostructures. Select High-frequency enhancement-mode millimeterwave AlGaN/GaN HEMT with an fT/fmax over 100 GHz/200 GHz Sheng Wu(武盛), Minhan Mi(宓珉瀚), Xiaohua Ma(马晓华), Ling Yang(杨凌), Bin Hou(侯斌), and Yue Hao(郝跃) Chin. Phys. B, 2021, 30 (8): 087102.   DOI: 10.1088/1674-1056/ac04a5 Abstract （557）   HTML （2）    PDF （1074KB）（178）       Knowledge map    Ultra-thin barrier (UTB) 4-nm-AlGaN/GaN normally-off high electron mobility transistors (HEMTs) having a high current gain cut-off frequency (fT) are demonstrated by the stress-engineered compressive SiN trench technology. The compressive in-situ SiN guarantees the UTB-AlGaN/GaN heterostructure can operate a high electron density of 1.27×1013cm-2, a high uniform sheet resistance of 312.8 Ω /□, but a negative threshold for the short-gate devices fabricated on it. With the lateral stress-engineering by full removing in-situ SiN in the 600-nm SiN trench, the short-gated (70 nm) devices obtain a threshold of 0.2 V, achieving the devices operating at enhancement-mode (E-mode). Meanwhile, the novel device also can operate a large current of 610 mA/mm and a high transconductance of 394 mS/mm for the E-mode devices. Most of all, a high fT/fmax of 128 GHz/255 GHz is obtained, which is the highest value among the reported E-mode AlGaN/GaN HEMTs. Besides, being together with the 211 GHz/346 GHz of fT/fmax for the D-mode HEMTs fabricated on the same materials, this design of E/D-mode with the realization of fmax over 200 GHz in this work is the first one that can be used in Q-band mixed-signal application with further optimization. And the minimized processing difference between the E- and D-mode designs the addition of the SiN trench, will promise an enormous competitive advantage in the fabricating costs. Select Observation of nonlinearity and heating-induced frequency shifts in cavity magnonics 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 （543）   HTML （3）    PDF （1892KB）（467）       Knowledge map    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. Select Efficiency droop in InGaN/GaN-based LEDs with a gradually varying In composition in each InGaN well layer Shang-Da Qu(屈尚达), Ming-Sheng Xu(徐明升), Cheng-Xin Wang(王成新), Kai-Ju Shi(时凯居), Rui Li(李睿), Ye-Hui Wei(魏烨辉), Xian-Gang Xu(徐现刚), and Zi-Wu Ji(冀子武) Chin. Phys. B, 2022, 31 (1): 017801.   DOI: 10.1088/1674-1056/ac0817 Abstract （542）   HTML （8）    PDF （547KB）（94）       Knowledge map    Temperature-dependent and driving current-dependent electroluminescence spectra of two different InGaN/GaN multiple quantum well structures SA and SB are investigated, with the In composition in each well layer (WL) along the growth direction progressively increasing for SA and progressively decreasing for SB. The results show that SB exhibits an improved efficiency droop compared with SA. This phenomenon can be explained as follows: owing to the difference in growth pattern of the WL between these two samples, the terminal region of the WL in SB contains fewer In atoms than in SA, and therefore the former undergoes less In volatilization than the latter during the waiting period required for warming-up due to the difference in the growth temperature between well and barrier layers. This results in SB having a deeper triangular-shaped potential well in its WL than SA, which strongly confines the carriers to the initial region of the WL to prevent them from leaking to the p-GaN side, thus improving the efficiency droop. Moreover, the improvement in the efficiency droop for SB is also partly attributed to its stronger Coulomb screening effect and carrier localization effect. Select Electric and thermal transport properties of topological insulator candidate LiMgBi Hao OuYang(欧阳豪), Qing-Xin Dong(董庆新), Yi-Fei Huang(黄奕飞), Jun-Sen Xiang(项俊森), Li-Bo Zhang(张黎博), Chen-Sheng Li(李晨圣), Pei-Jie Sun(孙培杰), Zhi-An Ren(任治安), and Gen-Fu Chen(陈根富) Chin. Phys. B, 2021, 30 (12): 127101.   DOI: 10.1088/1674-1056/ac009f Abstract （542）   HTML （2）    PDF （3091KB）（200）       Knowledge map    We report the transport properties of a topological insulator candidate, LiMgBi. The electric resistivity of the title compound exhibits a metal-to-semiconductor-like transition at around 160 K and tends to saturation below 50 K. At low temperatures, the magnetoresistance is up to ~260% at 9 T and a clear weak antilocalization effect is observed in the low magnetic-field region. The Hall measurement reveals that LiMgBi is a multiband system, where hole-type carriers (nh~1018 cm-3) play a major role in the transport process. Remarkably, LiMgBi possess a large Seebeck coefficient (~440 μV/K) and a moderate thermal conductivity at room temperature, which indicate that LiMgBi is a promising candidate in thermoelectric applications. Select Pressure-induced anomalous insulating behavior in frustrated iridate La3Ir3O11 Chun-Hua Chen(陈春华), Yong-Hui Zhou(周永惠), Ying Zhou(周颖), Yi-Fang Yuan(袁亦方), Chao An(安超), Xu-Liang Chen(陈绪亮), Zhao-Ming Tian(田召明), and Zhao-Rong Yang(杨昭荣) Chin. Phys. B, 2021, 30 (6): 067402.   DOI: 10.1088/1674-1056/abf100 Abstract （537）   HTML （1）    PDF （1106KB）（138）       Knowledge map    The geometrically frustrated iridate La3Ir3O11 with strong spin-orbit coupling and fractional valence was recently predicted to be a quantum spin liquid candidate at ambient conditions. Here, we systematically investigate the evolution of structural and electronic properties of La3Ir3O11 under high pressure. Electrical transport measurements reveal an abnormal insulating behavior rather than metallization above a critical pressure Pc ~38.7 GPa. Synchrotron x-ray diffraction (XRD) experiments indicate the stability of the pristine cubic KSbO3-type structure up to 73.1 GPa. Nevertheless, when the pressure gradually increases across Pc, the bulk modulus gets enhanced and the pressure dependence of bond length dIr-Ir undergoes a slope change. Consistent with the XRD data, detailed analyses of Raman spectra reveal an abnormal redshift of Raman mode and a change of Raman intensity around Pc. Our results demonstrate that the pressure-induced insulating behavior in La3Ir3O11 can be assigned to the structural modification, such as the distortion of IrO6 octahedra. These findings will shed light on the emergent abnormal insulating behavior in other 5d iridates reported recently. Select Non-Hermitian Kitaev chain with complex periodic and quasiperiodic potentials Xiang-Ping Jiang(蒋相平), Yi Qiao(乔艺), and Junpeng Cao(曹俊鹏) Chin. Phys. B, 2021, 30 (7): 077101.   DOI: 10.1088/1674-1056/abfa08 Abstract （515）   HTML （6）    PDF （963KB）（205）       Knowledge map    We study the topological properties of the one-dimensional non-Hermitian Kitaev model with complex either periodic or quasiperiodic potentials. We obtain the energy spectrum and the phase diagrams of the system by using the transfer matrix method as well as the topological invariant. The phase transition points are given analytically. The Majorana zero modes in the topological nontrivial regimes are obtained. Focusing on the quasiperiodic potential, we obtain the phase transition from the topological superconducting phase to the Anderson localization, which is accompanied with the Anderson localization-delocalization transition in this non-Hermitian system. We also find that the topological regime can be reduced by increasing the non-Hermiticity. Select Effects of post-annealing on crystalline and transport properties of Bi2Te3 thin films Qi-Xun Guo(郭奇勋), Zhong-Xu Ren(任中旭), Yi-Ya Huang(黄意雅), Zhi-Chao Zheng(郑志超), Xue-Min Wang(王学敏), Wei He(何为), Zhen-Dong Zhu(朱振东), and Jiao Teng(滕蛟) Chin. Phys. B, 2021, 30 (6): 067307.   DOI: 10.1088/1674-1056/abee6c Abstract （514）   HTML （1）    PDF （1874KB）（175）       Knowledge map    A well-established method is highly desirable for growing topological insulator thin films with low carrier density on a wafer-level scale. Here, we present a simple, scalable method based on magnetron sputtering to obtain high-quality Bi2Te3 films with the carrier density down to 4.0×1013 cm-2. In contrast to the most-used method of high substrate temperature growth, we firstly sputtered Bi2Te3 thin films at room temperature and then applied post-annealing. It enables the growth of highly-oriented Bi2Te3 thin films with larger grain size and smoother interface. The results of electrical transport show that it has a lower carrier density as well as a larger coherent length (~228 nm, 2 K). Our studies pave the way toward large-scale, cost-effective production of Bi2Te3 thin films to be integrated with other materials in wafer-level scale for electronic and spintronic applications. Select Tuning energy transfer efficiency in quantum dots mixture by controling donor/acceptor ratio Chang Liu(刘畅), Jing Liang(梁晶), Fangfang Wang(王芳芳), Chaojie Ma(马超杰), Kehai Liu(刘科海), Can Liu(刘灿), Hao Hong(洪浩), Huaibin Shen(申怀彬), Kaihui Liu(刘开辉), and Enge Wang(王恩哥) Chin. Phys. B, 2021, 30 (12): 127802.   DOI: 10.1088/1674-1056/ac29b2 Abstract （509）   HTML （2）    PDF （1299KB）（224）       Knowledge map    Improving the emission performance of colloidal quantum dots (QDs) is of paramount importance for their applications on light-emitting diodes (LEDs), displays and lasers. A highly promising approach is to tune the carrier recombination channels and lifetime by exploiting the energy transfer process. However, to achieve this precise emission optimization, quantitative modulation on energy transfer efficiency is highly desirable but still challenging. Here, we demonstrate a convenient approach to realize tunable energy transfer efficiency by forming QDs mixture with controllable donor/acceptor (D/A) ratio. With the mixing ratio ranging from 16/1 to 1/16, the energy transfer efficiency could be effectively tuned from near zero to ~70%. For the high mixing ratio of 16/1, acceptors obtain adequate energy supplied by closely surrounding donors, leading to~2.4-fold PL enhancement. While for the low mixing ratio, the ultrafast and efficient energy extraction process directly suppresses the multi-exciton and Auger recombination in the donor, bringing about a higher threshold. The facile modulation of emission performance by controllably designed mixing ratio and quantitatively tunable energy transfer efficiency will facilitate QD-based optoelectronic and photovoltaic applications. Select Tuning charge and orbital ordering in DyNiO3 by biaxial strain Litong Jiang(姜丽桐), Kuijuan Jin(金奎娟), Wenning Ren(任文宁), and Guozhen Yang(杨国桢) Chin. Phys. B, 2021, 30 (11): 117106.   DOI: 10.1088/1674-1056/abfbcf Abstract （507）   HTML （0）    PDF （1750KB）（110）       Knowledge map    The first-principles calculations were used to explore the tunable electronic structure in DyNiO3 (DNO) under the effects of the biaxial compressive and tensile strains. We explored how the biaxial strain tunes the orbital hybridization and influences the charge and orbital ordering states. We found that breathing mode and Jahn-Teller distortion play a primary role in charge ordering state and orbital ordering state, respectively. Additionally, the calculated results revealed that the biaxial strain has the ability to manipulate the phase competition between the two states. A phase transition point has been found under tensile train. If the biaxial train is larger than the point, the system favors orbital ordering state. If the strain is smaller than the point, the system is in charge ordering state favorably. Select Magnetic dynamics of two-dimensional itinerant ferromagnet Fe3GeTe2 Lijun Ni(倪丽君), Zhendong Chen(陈振东), Wei Li(李威), Xianyang Lu(陆显扬), Yu Yan(严羽), Longlong Zhang(张龙龙), Chunjie Yan(晏春杰), Yang Chen(陈阳), Yaoyu Gu(顾耀玉), Yao Li(黎遥), Rong Zhang(张荣), Ya Zhai(翟亚), Ronghua Liu(刘荣华), Yi Yang(杨燚), and Yongbing Xu(徐永兵) Chin. Phys. B, 2021, 30 (9): 097501.   DOI: 10.1088/1674-1056/ac0e25 Abstract （504）   HTML （3）    PDF （932KB）（343）       Knowledge map    Among the layered two-dimensional ferromagnetic materials (2D FMs), due to a relatively high TC, the van der Waals (vdW) Fe3GeTe2 (FGT) crystal is of great importance for investigating its distinct magnetic properties. Here, we have carried out static and dynamic magnetization measurements of the FGT crystal with a Curie temperature TC ≈ 204 K. The M-H hysteresis loops with in-plane and out-of-plane orientations show that FGT has a strong perpendicular magnetic anisotropy with the easy axis along its c-axis. Moreover, we have calculated the uniaxial magnetic anisotropy constant (K1) from the SQUID measurements. The dynamic magnetic properties of FGT have been probed by utilizing the high sensitivity electron-spin-resonance (ESR) spectrometer at cryogenic temperatures. Based on an approximation of single magnetic domain mode, the K1 and the effective damping constant (αeff) have also been determined from the out-of-plane angular dependence of ferromagnetic resonance (FMR) spectra obtained at the temperature range of 185 K to TC. We have found large magnetic damping with the effective damping constant αeff～ 0.58 along with a broad linewidth (ΔHpp> 1000 Oe at 9.48 GHz, H||c-axis). Our results provide useful dynamics information for the development of FGT-based spintronic devices. Select Design and simulation of AlN-based vertical Schottky barrier diodes Chun-Xu Su(苏春旭), Wei Wen(温暐), Wu-Xiong Fei(费武雄), Wei Mao(毛维), Jia-Jie Chen(陈佳杰), Wei-Hang Zhang(张苇杭), Sheng-Lei Zhao(赵胜雷), Jin-Cheng Zhang(张进成), and Yue Hao(郝跃) Chin. Phys. B, 2021, 30 (6): 067305.   DOI: 10.1088/1674-1056/abe0c7 Abstract （503）   HTML （5）    PDF （879KB）（105）       Knowledge map    The key parameters of vertical AlN Schottky barrier diodes (SBDs) with variable drift layer thickness (DLT) and drift layer concentration (DLC) are investigated. The specific on-resistance (Ron,sp) decreased to 0.5 mΩ·cm2 and the breakdown voltage (VBR) decreased from 3.4 kV to 1.1 kV by changing the DLC from 1015 cm-3 to 3×1016 cm-3. The VBR increases from 1.5 kV to 3.4 kV and the Ron,sp also increases to 12.64 mΩ·cm2 by increasing DLT from 4-μ to 11-μ. The VBR enhancement results from the increase of depletion region extension. The Baliga's figure of merit (BFOM) of 3.8 GW/cm2 was obtained in the structure of 11-μ DLT and 1016 cm-3 DLC without FP. When DLT or DLC is variable, the consideration of the value of BFOM is essential. In this paper, we also present the vertical AlN SBD with a field plate (FP), which decreases the crowding of electric field in electrode edge. All the key parameters were optimized by simulating based on Silvaco-ATLAS. page Page 1 of 24 Total 468 records First page Prev page Next page Last page