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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 Ultrafast structural dynamics using time-resolved x-ray diffraction driven by relativistic laser pulses Chang-Qing Zhu(朱常青), Jun-Hao Tan(谭军豪), Yu-Hang He(何雨航), Jin-Guang Wang(王进光), Yi-Fei Li(李毅飞), Xin Lu(鲁欣), Ying-Jun Li(李英骏), Jie Chen(陈洁), Li-Ming Chen(陈黎明), and Jie Zhang(张杰) Chin. Phys. B, 2021, 30 (9): 098701.   DOI: 10.1088/1674-1056/ac0baf Abstract （910）   HTML （6）    PDF （2226KB）（427）       Knowledge map    Based on a femtosecond laser plasma-induced hard x-ray source with a high laser pulse energy (>100 mJ) at 10 Hz repetition rate, we present a time-resolved x-ray diffraction system on an ultrafast time scale. The laser intensity is at relativistic regime (2×1019 W/cm2), which is essential for effectively generating Kα source in high-Z metal material. The produced copper Kα radiation yield reaches to 2.5×108 photons/sr/shot. The multilayer mirrors are optimized for monochromatizating and two-dimensional beam shaping of Kα emission. Our experiment exhibits its ability of monitoring the transient structural changes in a thin film SrCoO2.5 crystal. It is demonstrated that this facility is a powerful tool to perform dynamic studies on samples and adaptable to the specific needs for different particular applications with high flexibility. Select Widely tunable single-photon source with high spectral-purity from telecom wavelength to mid-infrared wavelength based on MgO:PPLN Chang-Wei Sun(孙昌伟), Yu Sun(孙宇), Jia-Chen Duan(端家晨), Guang-Tai Xue(薛广太), Yi-Chen Liu(刘奕辰), Liang-Liang Lu(陆亮亮), Qun-Yong Zhang(张群永), Yan-Xiao Gong(龚彦晓), Ping Xu(徐平), and Shi-Ning Zhu(祝世宁) Chin. Phys. B, 2021, 30 (10): 100312.   DOI: 10.1088/1674-1056/ac20cb Abstract （908）   HTML （4）    PDF （1543KB）（698）       Knowledge map    By utilizing the extended phase-matching (EPM) method, we investigate the generation of single photons with high spectral-purity in a magnesium-doped periodically-poled lithium niobate (MgO:PPLN) crystal via the spontaneous parametric down-conversion (SPDC) process. By adjusting the temperature and pump wavelength, the wavelength of the single photons can be tuned from telecom to mid-infrared (MIR) wavelengths, for which the spectral-purity can be above 0.95 with high transmission filters. In experiments, we engineer a MgO:PPLN with poling period of 20.35 μ which emits the EPM photon pair centered at 1496.6 nm and 1644.0 nm and carry out the joint spectral intensity (JSI) and Glauber's second-order self-correlation measurements to characterize the spectral purity. The results are in good agreement with the numerical simulations. Our work may provide a valuable approach for the generation of spectrally pure single photons at a wide range of wavelengths which is competent for various photonic quantum technologies. Select Discontinuous and continuous transitions of collective behaviors in living systems Xu Li(李旭), Tingting Xue(薛婷婷), Yu Sun(孙宇), Jingfang Fan(樊京芳), Hui Li(李辉), Maoxin Liu(刘卯鑫), Zhangang Han(韩战钢), Zengru Di(狄增如), and Xiaosong Chen(陈晓松) Chin. Phys. B, 2021, 30 (12): 128703.   DOI: 10.1088/1674-1056/ac3c3f Abstract （878）   HTML （9）    PDF （1918KB）（557）       Knowledge map    Living systems are full of astonishing diversity and complexity of life. Despite differences in the length scales and cognitive abilities of these systems, collective motion of large groups of individuals can emerge. It is of great importance to seek for the fundamental principles of collective motion, such as phase transitions and their natures. Via an eigen microstate approach, we have found a discontinuous transition of density and a continuous transition of velocity in the Vicsek models of collective motion, which are identified by the finite-size scaling form of order-parameter. At strong noise, living systems behave like gas. With the decrease of noise, the interactions between the particles of a living system become stronger and make them come closer. The living system experiences then a discontinuous gas-liquid like transition of density. The even stronger interactions at smaller noise make the velocity directions of the particles become ordered and there is a continuous phase transition of collective motion in addition. Select Unusual electronic structure of Dirac material BaMnSb2 revealed by angle-resolved photoemission spectroscopy Hongtao Rong(戎洪涛), Liqin Zhou(周丽琴), Junbao He(何俊宝), Chunyao Song(宋春尧), Yu Xu(徐煜), Yongqing Cai(蔡永青), Cong Li(李聪), Qingyan Wang(王庆艳), Lin Zhao(赵林), Guodong Liu(刘国东), Zuyan Xu(许祖彦), Genfu Chen(陈根富), Hongming Weng(翁红明), and Xingjiang Zhou(周兴江) Chin. Phys. B, 2021, 30 (6): 067403.   DOI: 10.1088/1674-1056/ac0036 Abstract （828）   HTML （1）    PDF （2780KB）（380）       Knowledge map    High resolution angle resolved photoemission measurements and band structure calculations are carried out to study the electronic structure of BaMnSb2. All the observed bands are nearly linear that extend to a wide energy range. The measured Fermi surface mainly consists of one hole pocket around Γ and a strong spot at Y which are formed from the crossing points of the linear bands. The measured electronic structure of BaMnSb2 is unusual and deviates strongly from the band structure calculations. These results will stimulate further efforts to theoretically understand the electronic structure of BaMnSb2 and search for novel properties in this Dirac material. Select A double quantum dot defined by top gates in a single crystalline InSb nanosheet Yuanjie Chen(陈元杰), Shaoyun Huang(黄少云), Jingwei Mu(慕经纬), Dong Pan(潘东), Jianhua Zhao(赵建华), and Hong-Qi Xu(徐洪起) Chin. Phys. B, 2021, 30 (12): 128501.   DOI: 10.1088/1674-1056/abff2e Abstract （802）   HTML （2）    PDF （1960KB）（495）       Knowledge map    We report on the transport study of a double quantum dot (DQD) device made from a freestanding, single crystalline InSb nanosheet. The freestanding nanosheet is grown by molecular beam epitaxy and the DQD is defined by the top gate technique. Through the transport measurements, we demonstrate how a single quantum dot (QD) and a DQD can be defined in an InSb nanosheet by tuning voltages applied to the top gates. We also measure the charge stability diagrams of the DQD and show that the charge states and the inter-dot coupling between the two individual QDs in the DQD can be efficiently regulated by the top gates. Numerical simulations for the potential profile and charge density distribution in the DQD have been performed and the results support the experimental findings and provide a better understanding of fabrication and transport characteristics of the DQD in the InSb nanosheet. The achieved DQD in the two-dimensional InSb nanosheet possesses pronounced benefits in lateral scaling and can thus serve as a new building block for the developments of quantum computation and quantum simulation technologies. Select Magneto-transport properties of thin flakes of Weyl semiconductor tellurium Nan Zhang(张南), Bin Cheng(程斌), Hui Li(李惠), Lin Li(李林), and Chang-Gan Zeng(曾长淦) Chin. Phys. B, 2021, 30 (8): 087304.   DOI: 10.1088/1674-1056/ac0a5e Abstract （782）   HTML （23）    PDF （7248KB）（530）       Knowledge map    As an elemental semiconductor, tellurium has recently attracted intense interest due to its non-trivial band topology, and the resulted intriguing topological transport phenomena. In this study we report systematic electronic transport studies on tellurium flakes grown via a simple vapor deposition process. The sample is self-hole-doped, and exhibits typical weak localization behavior at low temperatures. Substantial negative longitudinal magnetoresistance under parallel magnetic field is observed over a wide temperature region, which is considered to share the same origin with that in tellurium bulk crystals, i.e., the Weyl points near the top of valence band. However, with lowering temperature the longitudinal magnetoconductivity experiences a transition from parabolic to linear field dependency, differing distinctly from the bulk counterparts. Further analysis reveals that such a modulation of Weyl behaviors in this low-dimensional tellurium structure can be attributed to the enhanced inter-valley scattering at low temperatures. Our results further extend Weyl physics into a low-dimensional semiconductor system, which may find its potential application in designing topological semiconductor devices. Select Measuring Loschmidt echo via Floquet engineering in superconducting circuits Shou-Kuan Zhao(赵寿宽), Zi-Yong Ge(葛自勇), Zhong-Cheng Xiang(相忠诚), Guang-Ming Xue(薛光明), Hai-Sheng Yan(严海生), Zi-Ting Wang(王子婷), Zhan Wang(王战), Hui-Kai Xu(徐晖凯), Fei-Fan Su(宿非凡), Zhao-Hua Yang(杨钊华), He Zhang(张贺), Yu-Ran Zhang(张煜然), Xue-Yi Guo(郭学仪), Kai Xu(许凯), Ye Tian(田野), Hai-Feng Yu(于海峰), Dong-Ning Zheng(郑东宁), Heng Fan(范桁), and Shi-Ping Zhao(赵士平) Chin. Phys. B, 2022, 31 (3): 030307.   DOI: 10.1088/1674-1056/ac40f8 Abstract （781）   HTML （4）    PDF （1107KB）（601）       Knowledge map    The Loschmidt echo is a useful diagnostic for the perfection of quantum time-reversal process and the sensitivity of quantum evolution to small perturbations. The main challenge for measuring the Loschmidt echo is the time reversal of a quantum evolution. In this work, we demonstrate the measurement of the Loschmidt echo in a superconducting 10-qubit system using Floquet engineering and discuss the imperfection of an initial Bell-state recovery arising from the next-nearest-neighbor (NNN) coupling present in the qubit device. Our results show that the Loschmidt echo is very sensitive to small perturbations during quantum-state evolution, in contrast to the quantities like qubit population that is often considered in the time-reversal experiment. These properties may be employed for the investigation of multiqubit system concerning many-body decoherence and entanglement, etc., especially when devices with reduced or vanishing NNN coupling are used. Select Gate-controlled magnetic transitions in Fe3GeTe2 with lithium ion conducting glass substrate Guangyi Chen(陈光毅), Yu Zhang(张玉), Shaomian Qi(齐少勉), and Jian-Hao Chen(陈剑豪) Chin. Phys. B, 2021, 30 (9): 097504.   DOI: 10.1088/1674-1056/ac1338 Abstract （778）   HTML （4）    PDF （806KB）（600）       Knowledge map    Since the discovery of magnetism in two dimensions, effective manipulation of magnetism in van der Waals magnets has always been a crucial goal. Ionic gating is a promising method for such manipulation, yet devices gated with conventional ionic liquid may have some restrictions in applications due to the liquid nature of the gate dielectric. Lithium-ion conducting glass-ceramics (LICGC), a solid Li+ electrolyte, could be used as a substrate while simultaneously acts as a promising substitute for ionic liquid. Here we demonstrate that the ferromagnetism of Fe3GeTe2 (FGT) could be modulated via LICGC. By applying a voltage between FGT and the back side of LICGC substrate, Li+ doping occurs and causes the decrease of the coercive field (Hc) and ferromagnetic transition temperature (Tc) in FGT nanoflakes. A modulation efficiency for Hc of up to ～ 24.6% under Vg = 3.5 V at T =100 K is achieved. Our results provide another method to construct electrically-controlled magnetoelectronics, with potential applications in future information technology. Select Direct visualization of structural defects in 2D semiconductors Yutuo Guo(郭玉拓), Qinqin Wang(王琴琴), Xiaomei Li(李晓梅), Zheng Wei(魏争), Lu Li(李璐), Yalin Peng(彭雅琳), Wei Yang(杨威), Rong Yang(杨蓉), Dongxia Shi(时东霞), Xuedong Bai(白雪冬), Luojun Du(杜罗军), and Guangyu Zhang(张广宇) Chin. Phys. B, 2022, 31 (7): 076105.   DOI: 10.1088/1674-1056/ac6738 Abstract （771）   HTML （43）    PDF （4731KB）（479）       Knowledge map    Direct visualization of the structural defects in two-dimensional (2D) semiconductors at a large scale plays a significant role in understanding their electrical/optical/magnetic properties, but is challenging. Although traditional atomic resolution imaging techniques, such as transmission electron microscopy and scanning tunneling microscopy, can directly image the structural defects, they provide only local-scale information and require complex setups. Here, we develop a simple, non-invasive wet etching method to directly visualize the structural defects in 2D semiconductors at a large scale, including both point defects and grain boundaries. Utilizing this method, we extract successfully the defects density in several different types of monolayer molybdenum disulfide samples, providing key insights into the device functions. Furthermore, the etching method we developed is anisotropic and tunable, opening up opportunities to obtain exotic edge states on demand. Select First neutron Bragg-edge imaging experimental results at CSNS Jie Chen(陈洁), Zhijian Tan(谭志坚), Weiqiang Liu(刘玮强), Sihao Deng(邓司浩), Shengxiang Wang(王声翔), Liyi Wang(王立毅), Haibiao Zheng(郑海彪), Huaile Lu(卢怀乐), Feiran Shen(沈斐然), Jiazheng Hao(郝嘉政), Xiaojuan Zhou(周晓娟), Jianrong Zhou(周健荣), Zhijia Sun(孙志嘉), Lunhua He(何伦华), and Tianjiao Liang(梁天骄) Chin. Phys. B, 2021, 30 (9): 096106.   DOI: 10.1088/1674-1056/ac0da7 Abstract （770）   HTML （6）    PDF （1294KB）（470）       Knowledge map    The neutron Bragg-edge imaging is expected to be a new non-destructive energy-resolved neutron imaging technique for quantitatively two-dimensional or three-dimensional visualizing crystallographic information in a bulk material, which could be benefited from pulsed neutron source. Here we build a Bragg-edge imaging system on the General Purpose Powder Diffractometer at the China Spallation Neutron Source. The residual strain mapping of a bent Q235 ferrite steel sample has been achieved with a spectral resolution of 0.15% by the time-of-flight neutron Bragg-edge imaging on this system. The results show its great potential applications in materials science and engineering. Select A composite micromotor driven by self-thermophoresis and Brownian rectification Xin Lou(娄辛), Nan Yu(余楠), Ke Chen(陈科), Xin Zhou(周昕), Rudolf Podgornik, and Mingcheng Yang(杨明成) Chin. Phys. B, 2021, 30 (11): 114702.   DOI: 10.1088/1674-1056/ac2727 Abstract （712）   HTML （1）    PDF （517KB）（482）       Knowledge map    Brownian motors and self-phoretic microswimmers are two typical micromotors, for which thermal fluctuations play different roles. Brownian motors utilize thermal noise to acquire unidirectional motion, while thermal fluctuations randomize the self-propulsion of self-phoretic microswimmers. Here we perform mesoscale simulations to study a composite micromotor composed of a self-thermophoretic Janus particle under a time-modulated external ratchet potential. The composite motor exhibits a unidirectional transport, whose direction can be reversed by tuning the modulation frequency of the external potential. The maximum transport capability is close to the superposition of the drift speed of the pure Brownian motor and the self-propelling speed of the pure self-thermophoretic particle. Moreover, the hydrodynamic effect influences the orientation of the Janus particle in the ratched potential, hence also the performance of the composite motor. Our work thus provides an enlightening attempt to actively exploit inevitable thermal fluctuations in the implementation of the self-phoretic microswimmers. Select Electronic structure and spin–orbit coupling in ternary transition metal chalcogenides Cu2TlX2 (X = Se, Te) Na Qin(秦娜), Xian Du(杜宪), Yangyang Lv(吕洋洋), Lu Kang(康璐), Zhongxu Yin(尹中旭), Jingsong Zhou(周景松), Xu Gu(顾旭), Qinqin Zhang(张琴琴), Runzhe Xu(许润哲), Wenxuan Zhao(赵文轩), Yidian Li(李义典), Shuhua Yao(姚淑华), Yanfeng Chen(陈延峰), Zhongkai Liu(柳仲楷), Lexian Yang(杨乐仙), and Yulin Chen(陈宇林) Chin. Phys. B, 2022, 31 (3): 037101.   DOI: 10.1088/1674-1056/ac3ecd Abstract （670）   HTML （4）    PDF （5919KB）（476）       Knowledge map    Ternary transition metal chalcogenides provide a rich platform to search and study intriguing electronic properties. Using angle-resolved photoemission spectroscopy and ab initio calculation, we investigate the electronic structure of Cu$_{2}$Tl$X_{2}$ ($X=\text{Se, Te}$), ternary transition metal chalcogenides with quasi-two-dimensional crystal structure. The band dispersions near the Fermi level are mainly contributed by the Te/Se p orbitals. According to our ab-initio calculation, the electronic structure changes from a semiconductor with indirect band gap in Cu$_{2}$TlSe$_{2}$ to a semimetal in Cu$_{2}$TlTe$_{2}$, suggesting a band-gap tunability with the composition of Se and Te. By comparing ARPES experimental data with the calculated results, we identify strong modulation of the band structure by spin-orbit coupling in the compounds. Our results provide a ternary platform to study and engineer the electronic properties of transition metal chalcogenides related to large spin-orbit coupling. Select The 50 nm-thick yttrium iron garnet films with perpendicular magnetic anisotropy Shuyao Chen(陈姝瑶), Yunfei Xie(谢云飞), Yucong Yang(杨玉聪), Dong Gao(高栋), Donghua Liu(刘冬华), Lin Qin(秦林), Wei Yan(严巍), Bi Tan(谭碧), Qiuli Chen(陈秋丽), Tao Gong(龚涛), En Li(李恩), Lei Bi(毕磊), Tao Liu(刘涛), and Longjiang Deng(邓龙江) Chin. Phys. B, 2022, 31 (4): 048503.   DOI: 10.1088/1674-1056/ac4cc4 Abstract （670）   HTML （1）    PDF （1413KB）（323）       Knowledge map    Yttrium iron garnet (YIG) films possessing both perpendicular magnetic anisotropy (PMA) and low damping would serve as ideal candidates for high-speed energy-efficient spintronic and magnonic devices. However, it is still challenging to achieve PMA in YIG films thicker than 20 nm, which is a major bottleneck for their development. In this work, we demonstrate that this problem can be solved by using substrates with moderate lattice mismatch with YIG so as to suppress the excessive strain-induced stress release as increasing the YIG thickness. After carefully optimizing the growth and annealing conditions, we have achieved out-of-plane spontaneous magnetization in YIG films grown on sGGG substrates, even when they are as thick as 50 nm. Furthermore, ferromagnetic resonance and spin pumping induced inverse spin Hall effect measurements further verify the good spin transparency at the surface of our YIG films. Select Topological Dirac surface states in ternary compounds GeBi2Te4, SnBi2Te4 and Sn0.571Bi2.286Se4 Yunlong Li(李云龙), Chaozhi Huang(黄超之), Guohua Wang(王国华), Jiayuan Hu(胡佳元), Shaofeng Duan(段绍峰), Chenhang Xu(徐晨航), Qi Lu(卢琦), Qiang Jing(景强), Wentao Zhang(张文涛), and Dong Qian(钱冬) Chin. Phys. B, 2021, 30 (12): 127901.   DOI: 10.1088/1674-1056/ac2b92 Abstract （670）   HTML （0）    PDF （1041KB）（369）       Knowledge map    Using high-resolution angle-resolved and time-resolved photoemission spectroscopy, we have studied the low-energy band structures in occupied and unoccupied states of three ternary compounds GeBi2Te4, SnBi2Te4 and Sn0.571Bi2.286Se4 near the Fermi level. In previously confirmed topological insulator GeBi2Te4 compounds, we confirmed the existence of the Dirac surface state and found that the bulk energy gap is much larger than that in the first-principles calculations. In SnBi2Te4 compounds, the Dirac surface state was observed, consistent with the first-principles calculations, indicating that it is a topological insulator. The experimental detected bulk gap is a little bit larger than that in calculations. In Sn0.571Bi2.286Se4 compounds, our measurements suggest that this nonstoichiometric compound is a topological insulator although the stoichiometric SnBi2Se4 compound was proposed to be topological trivial. Select Bismuth doping enhanced tunability of strain-controlled magnetic anisotropy in epitaxial Y3Fe5O12(111) films Yunpeng Jia(贾云鹏), Zhengguo Liang(梁正国), Haolin Pan(潘昊霖), Qing Wang(王庆), Qiming Lv(吕崎鸣), Yifei Yan(严轶非), Feng Jin(金锋), Dazhi Hou(侯达之), Lingfei Wang(王凌飞), and Wenbin Wu(吴文彬) Chin. Phys. B, 2023, 32 (2): 027501.   DOI: 10.1088/1674-1056/ac67cc Abstract （640）   HTML （7）    PDF （893KB）（454）       Knowledge map    Y3Fe5O12 (YIG) and BiY2Fe5O12 (Bi:YIG) films were epitaxially grown on a series of (111)-oriented garnet substrates using pulsed laser deposition. Structural and ferromagnetic resonance characterizations demonstrated the high epitaxial quality, extremely low magnetic loss and coherent strain state in these films. Using these epitaxial films as model systems, we systematically investigated the evolution of magnetic anisotropy (MA) with epitaxial strain and chemical doping. For both the YIG and Bi:YIG films, the compressive strain tends to align the magnetic moment in the film plane while the tensile strain can compete with the demagnetization effect and stabilize perpendicular MA. We found that the strain-induced lattice elongation/compression along the out-of-plane [111] axis is the key parameter that determines the MA. More importantly, the strain-induced tunability of MA can be enhanced significantly by Bi doping; meanwhile, the ultralow damping feature persists. We clarified that the cooperation between strain and chemical doping could realize an effective control of MA in garnet-type ferrites, which is essential for spintronic applications. Select Monolayer MoS2 of high mobility grown on SiO2 substrate by two-step chemical vapor deposition Jia-Jun Ma(马佳俊), Kang Wu(吴康), Zhen-Yu Wang(王振宇), Rui-Song Ma(马瑞松), Li-Hong Bao(鲍丽宏), Qing Dai(戴庆), Jin-Dong Ren(任金东), and Hong-Jun Gao(高鸿钧) Chin. Phys. B, 2022, 31 (8): 088105.   DOI: 10.1088/1674-1056/ac6737 Abstract （635）   HTML （20）    PDF （1277KB）（463）       Knowledge map    We report a novel two-step ambient pressure chemical vapor deposition (CVD) pathway to grow high-quality MoS2 monolayer on the SiO2 substrate with large crystal size up to 110 μm. The large specific surface area of the pre-synthesized MoO3 flakes on the mica substrate compared to MoO3 powder could dramatically reduce the consumption of the Mo source. The electronic information inferred from the four-probe scanning tunneling microscope (4P-STM) image explains the threshold voltage variations and the n-type behavior observed in the two-terminal transport measurements. Furthermore, the direct van der Pauw transport also confirms its relatively high carrier mobility. Our study provides a reliable method to synthesize high-quality MoS2 monolayer, which is confirmed by the direct 4P-STM measurement results. Such methodology is a key step toward the large-scale growth of transition metal dichalcogenides (TMDs) on the SiO2 substrate and is essential to further development of the TMDs-related integrated devices. Select Reconstruction and functionalization of aerogels by controlling mesoscopic nucleation to greatly enhance macroscopic performance Chen-Lu Jiao(焦晨璐), Guang-Wei Shao(邵光伟), Yu-Yue Chen(陈宇岳), and Xiang-Yang Liu(刘向阳) Chin. Phys. B, 2023, 32 (3): 038103.   DOI: 10.1088/1674-1056/acb912 Abstract （635）   HTML （24）    PDF （7614KB）（554）       Knowledge map    This work presents a strategy for the mesoscopic engineering of hierarchically structured sodium alginate (SA) aerogels to enhance the macroscopic performance. The strategy was implemented by meso-functionalizing and reorganizing SA aerogels via controlled heterogeneous nucleation, in which microcrystalline cellulose-manganese dioxide (MCC-MnO2) nano-crystallites worked as template. Due to the short rod-like structure and abundant hydroxyl groups of MCC-MnO2, the organized mesostructure of SA aerogels was reconstructed during the assembly of SA molecule chains, which gave rise to a significant enhancement in macroscopic performance of SA areogels. For instance, the functionalized and reconstructed MCC-MnO2/SA aerogels acquired a more than 70% increase in mechanical strength with an excellent deformation recovery. Furthermore, an almost double enhancement of removal capacity for metal ions (i.e., Cu2+ and Pb2+) and organic dyes (i.e., congo red and methylene blue) was obtained for MnO2/SA aerogels, with an 87% repossession of the pollutants removal performance after 5 operation cycles. Select Powder x-ray diffraction and Rietveld analysis of (C2H5NH3)2CuCl4 Yi Liu(刘义), Jun Shen(沈俊), Zunming Lu(卢遵铭), Baogen Shen(沈保根), and Liqin Yan(闫丽琴) Chin. Phys. B, 2021, 30 (6): 067502.   DOI: 10.1088/1674-1056/abee0a Abstract （630）   HTML （1）    PDF （1515KB）（153）       Knowledge map    Structural properties of the organic-inorganic hybrid (C2H5NH3)2CuCl4 (EA2CuCl4) have been investigated by means of x-ray powder diffraction and Rietveld analysis. A structural phase transition from Pbca to Aba2 occurs at T4=240 K, which results in a paraelectric-ferroelectric phase transition. The release of the Jahn-Teller distortion with increasing temperature toward T4 is revealed by the structural analysis. Select Stabilization of formamidinium lead iodide perovskite precursor solution for blade-coating efficient carbon electrode perovskite solar cells Yu Zhan(占宇), Weijie Chen(陈炜杰), Fu Yang(杨甫), and Yaowen Li(李耀文) Chin. Phys. B, 2021, 30 (8): 088803.   DOI: 10.1088/1674-1056/abfbcb Abstract （630）   HTML （3）    PDF （4217KB）（382）       Knowledge map    Formamidinium lead triiodide (FAPbI3) is a research hotspot in perovskite photovoltaics due to its broad light absorption and proper thermal stability. However, quite a few researches focused on the stability of the FAPbI3 perovskite precursor solutions. Besides, the most efficient FAPbI3 layers are prepared by the spin-coating method, which is limited to the size of the device. Herein, the stability of FAPbI3 perovskite solution with methylammonium chloride (MACl) or cesium chloride (CsCl) additive is studied for preparing perovskite film through an upscalable blade-coating method. Each additive works well for achieving a high-quality FAPbI3 film, resulting in efficient carbon electrode perovskite solar cells (pero-SCs) in the ambient condition. However, the perovskite solution with MACl additive shows poor aging stability that no α-FAPbI3 phase is observed when the solution is aged over one week. While the perovskite solution with CsCl additive shows promising aging stability that it still forms high-quality pure α-FAPbI3 perovskite film even the solution is aged over one month. During the solution aging process, the MACl could be decomposed into methylamine which will form some unfavored intermediated phase inducing δ-phase FAPbI3. Whereas, replacing MACl with CsCl could effectively solve this issue. Our founding shows that there is a great need to develop a non-MACl FAPbI3 perovskite precursor solution for cost-effective preparation of pero-SCs. Select Excess-iron driven spin glass phase in Fe1+yTe1-xSex Long Tian(田龙), Panpan Liu(刘盼盼), Tao Hong(洪涛), Tilo Seydel, Xingye Lu(鲁兴业), Huiqian Luo(罗会仟), Shiliang Li(李世亮), and Pengcheng Dai(戴鹏程) Chin. Phys. B, 2021, 30 (8): 087402.   DOI: 10.1088/1674-1056/ac0695 Abstract （612）   HTML （0）    PDF （1310KB）（212）       Knowledge map    The iron-chalcogenide superconductor FeTe1-xSex displays a variety of exotic features distinct from iron pnictides. Although much effort has been devoted to understanding the interplay between magnetism and superconductivity near x=0.5, the existence of a spin glass phase with short-range magnetic order in the doping range (x～0.1-0.3) has rarely been studied. Here, we use DC/AC magnetization and (quasi) elastic neutron scattering to confirm the spin-glass nature of the short-range magnetic order in a Fe1.07Te0.8Se0.2 sample. The AC-frequency dependent spin-freezing temperature Tf generates a frequency sensitivity ΔTf(ω) /[Tf(ω) Δlog10ω]≈0.028 and the description of the critical slowing down with τ=τ0(Tf / TSG)-zv gives TSG≈22 K and zv≈10, comparable to that of a classical spin-glass system. We have also extended the frequency-dependent Tf to the smaller time scale using energy-resolution-dependent neutron diffraction measurements, in which the TN of the short-range magnetic order increases systematically with increasing energy resolution. By removing the excess iron through annealing in oxygen, the spin-freezing behavior disappears, and bulk superconductivity is realized. Thus, the excess Fe is the driving force for the formation of the spin-glass phase detrimental to bulk superconductivity. page Page 1 of 11 Total 203 records First page Prev page Next page Last page