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Implementation of Full Spin-State Interferometer
Peng-Ju Tang, Peng Peng, Xiang-Yu Dong, Xu-Zong Chen, Xiao-Ji Zhou
Chin. Phys. Lett. 2019, 36 (5):
050301
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DOI: 10.1088/0256-307X/36/5/050301
Matter-wave interferometers with spin quantum states are attractive in quantum manipulation and precision measurements. Here, five spatial interference patterns corresponding to the full spin states are observed in each run of the experiment, by the combination of the Majorana transition according to the exponential modulation of the magnetic field pulse decline curve and radio frequency coupling among multiple magnetic sub-states. Compared to the realization of two Majorana transitions, the interference fringe for the magnetic field insensitive state also has a higher contrast. After spatially overlapping the full magnetic sub-state interference patterns dozens of times in consecutive experimental measurements, clear fringes are still observed, indicating the great stability of the relative phases of different components. This indicates the potential to achieve an interferometer with multiple spin clocks.
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Improved Performance of a Wavelength-Tunable Arrayed Waveguide Grating in Silicon on Insulator
Pei Yuan, Xiao-Guang Zhang, Jun-Ming An, Peng-Gang Yin, Yue Wang, Yuan-Da Wu
Chin. Phys. Lett. 2019, 36 (5):
054204
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DOI: 10.1088/0256-307X/36/5/054204
The improved performance of a wavelength-tunable arrayed waveguide grating (AWG) is demonstrated, including the crosstalk, insertion loss and the wavelength tuning efficiency. A reduced impact of the fabrication process on the AWG is achieved by the design of bi-level tapers. The wavelength tuning of the AWG is achieved according to the thermo-optic effect of silicon, and uniform heating of the silicon waveguide layer is achieved by optimizing the heater design. The fabricated AWG shows a minimum crosstalk of 16 dB, a maximum insertion loss of 3.91 dB and a wavelength tuning efficiency of 8.92 nm/W, exhibiting a $\sim $8 dB improvement of crosstalk, $\sim $2.1 dB improvement of insertion loss and $\sim $5 nm/W improvement of wavelength tuning efficiency, compared to our previous reported results.
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Mechanical Properties of Formamidinium Halide Perovskites FABX$_{3}$ (FA=CH(NH$_{2})_{2}$; B=Pb, Sn; X=Br, I) by First-Principles Calculations
Lei Guo, Gang Tang, Jiawang Hong
Chin. Phys. Lett. 2019, 36 (5):
056201
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DOI: 10.1088/0256-307X/36/5/056201
The mechanical properties of formamidinium halide perovskites FABX$_{3}$ (FA=CH(NH$_{2})_{2}$; B=Pb, Sn; X=Br, I) are systematically investigated using first-principles calculations. Our results reveal that FABX$_{3}$ perovskites possess excellent mechanical flexibility, ductility and strong anisotropy. We shows that the planar organic cation FA$^{+}$ has an important effect on the mechanical properties of FABX$_{3}$ perovskites. In addition, our results indicate that (i) the moduli (bulk modulus $B$, Young's modulus $E$, and shear modulus $G$) of FABBr$_{3}$ are larger than those of FABI$_{3}$ for the same B atom, and (ii) the moduli of FAPbX$_{3}$ are larger than those of FASnX$_{3}$ for the same halide atom. The reason for the two trends is demonstrated by carefully analyzing the bond strength between B and X atoms based on the projected crystal orbital Hamilton population method.
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Negative Longitudinal Magnetoresistance in the $c$-Axis Resistivity of Cd
Xin-Min Wang, Ling-Xiao Zhao, Jing Li, Mo-Ran Gao, Wen-Liang Zhu, Chao-Yang Ma, Yi-Yan Wang, Shuai Zhang, Zhi-An Ren, Gen-Fu Chen
Chin. Phys. Lett. 2019, 36 (5):
057102
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DOI: 10.1088/0256-307X/36/5/057102
We report a systematic study on magnetotransport properties of the single crystal of cadmium (Cd). When the applied magnetic field $B$ is perpendicular to the current $I$, the resistivities for both directions ($I\parallel a$, $I \parallel c$) show field induced metal-to-insulator-like transitions. The isothermal magnetoresistance (MR) at low temperatures increases approximately as the square of the magnetic field without any sign of saturation, and reaches up to 1140000% and 58000% at $T=2$ K and $B=9$ T for $I\parallel a$ and $I\parallel c$, respectively. As the magnetic field rotates to parallel to the current, no sign of negative MR is observed for $I\parallel a$, while an obvious negative MR appears up to $-$70% at 2 K and 9 T for the current flowing along the $c$-axis, and the negative longitudinal MR shows a strong dependence of the electrode position on the single crystal. These results suggest that the negative longitudinal MR is caused by the dislocations formed in the process of crystal growing along the $c$-axis. Further studies are needed to clarify this point.
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Absorption Enhancement of Silicon Solar Cell in a Positive-Intrinsic-Negative Junction
Gen Yue, Zhen Deng, Sen Wang, Ran Xu, Xinxin Li, Ziguang Ma, Chunhua Du, Lu Wang, Yang Jiang, Haiqiang Jia, Wenxin Wang, Hong Chen
Chin. Phys. Lett. 2019, 36 (5):
057201
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DOI: 10.1088/0256-307X/36/5/057201
Absorption coefficient is a physical parameter to describe electromagnetic energy absorption of materials, which is closely related to solar cells and photodetectors. We grow a series of positive-intrinsic-negative (PIN) structures on silicon wafer by a gas source molecule beam epitaxy system and the investigate the absorption coefficient through the photovoltaic processes in detail. It is found that the absorption coefficient is enhanced by one order and can be tuned greatly through the thickness of the intrinsic layer in the PIN structure, which is also demonstrated by the 730-nm-wavelength laser irradiation. These results cannot be explained by the traditional absorption theory. We speculate that there could be some uncovered mechanism in this system, which will inspire us to understand the absorption process further.
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Dependence of Thermal Annealing on Transparent Conducting Properties of HoF$_{3}$-Doped ZnO Thin Films
Jin-Song Luo, Jie Lin, Li-Gong Zhang, Xiao-Yang Guo, Yong-Fu Zhu
Chin. Phys. Lett. 2019, 36 (5):
057303
.
DOI: 10.1088/0256-307X/36/5/057303
A kind of n-type HoF$_{3}$-doped zinc oxide-based transparent conductive film has been developed by electron beam evaporation and studied under thermal annealing in air and vacuum at temperatures 100–500$^{\circ}\!$C. Effective substitutional dopings of F to O and Ho to Zn are realized for the films with smooth surface morphology and average grain size of about 50 nm. The hall mobility, electron concentration, resistivity and work function for the as-deposited films are 47.89 cm$^{2}$/Vs, 1.39$\times 10^{20}$ cm$^{-3}$, $9.37\times 10^{-4}$ $\Omega$$\cdot$cm and 5.069 eV, respectively. In addition, the average transmittance in the visible region (400–700 nm) approximates to 87%. The HoF$_{3}$:ZnO films annealed in air and vacuum can retain good optoelectronic properties under 300$^{\circ}\!$C, thereinto, more stable electrical properties can be found in the air-annealed films than in the vacuum-annealed films, which is assumed to be a result of improved nano-crystalline lattice quality. The optimized films for most parameters can be obtained at 200$^{\circ}\!$C for the air-annealing case and at room temperature for the vacuum annealing case. The advisable optoelectronic properties imply that HoF$_{3}$:ZnO can facilitate carrier injection and has promising applications in energy and light sources as transparent electrodes.
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Growth of TlBa$_{2}$Ca$_{2}$Cu$_{3}$O$_{9}$ Epitaxial Thin Films by Two-Step Method in Argon
Jian Xing, Li-Tian Wang, Xiao-Xin Gao, Xue-Lian Liang, Kai-Yong He, Ting Xue, Sheng-Hui Zhao, Jin-Li Zhang, Ming He, Xin-Jie Zhao, Shao-Lin Yan, Pei Wang, Lu Ji
Chin. Phys. Lett. 2019, 36 (5):
057401
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DOI: 10.1088/0256-307X/36/5/057401
TlBa$_{2}$Ca$_{2}$Cu$_{3}$O$_{9}$ (Tl-1223) films have promising applications due to their high critical temperature and strong magnetic flux pinning. Nevertheless, the preparation of pure phase Tl-1223 film is still a challenge. We successfully fabricate Tl-1223 thin films on LaAlO$_{3}$ (001) substrates using dc magnetic sputtering and a post annealing two-step method in argon atmosphere. The crystallization temperature of Tl-1223 films in argon is reduced by 100$^{\circ}\!$C compared to that in oxygen. This greatly reduces the volatilization of Tl and improves the surface morphology of films. The lower annealing temperature can effectively improve the repeatability of the Tl-1223 film preparation. In addition, pure Tl-1223 phase can be obtained in a broad temperature zone, from 790$^{\circ}\!$C to 830$^{\circ}\!$C. In our study, the films show homogenous and dense surface morphology using the presented method. The best critical temperature of Tl-1223 films is characterized to be 110 K, and the critical current $J_{\rm c}$ (77 K, 0 T) is up to $2.13\times 10^{6}$ A/cm$^{2}$.
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Superconductivity and Fermi Surface Anisotropy in Transition Metal Dichalcogenide NbTe$_{2}$
Xi Zhang, Tianchuang Luo, Xiyao Hu, Jing Guo, Gongchang Lin, Yuehui Li, Yanzhao Liu, Xiaokang Li, Jun Ge, Ying Xing, Zengwei Zhu, Peng Gao, Liling Sun, Jian Wang
Chin. Phys. Lett. 2019, 36 (5):
057402
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DOI: 10.1088/0256-307X/36/5/057402
Transition metal dichalcogenides, featuring layered structures, have aroused enormous interest as a platform for novel physical phenomena and a wide range of potential applications. Among them, special interest has been placed upon WTe$_{2}$ and MoTe$_{2}$, which exhibit non-trivial topology both in single layer and bulk as well as pressure induced or enhanced superconductivity. We study another distorted 1T material NbTe$_{2}$ through systematic electrical transport measurements. Intrinsic superconductivity with onset transition temperature ($T_{\rm c}^{\rm onset}$) up to 0.72 K is detected where the upper critical field ($H_{\rm c}$) shows unconventional quasi-linear behavior, indicating spin-orbit coupling induced p-wave paring. Furthermore, a general model is proposed to fit the angle-dependent magnetoresistance, which reveals the Fermi surface anisotropy of NbTe$_{2}$. Finally, non-saturating linear magnetoresistance up to 50 T is observed and attributed to the quantum limit transport.
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Quantized Conductance of Majorana Zero Mode in the Vortex of the Topological Superconductor (Li$_{0.84}$Fe$_{0.16}$)OHFeSe
C. Chen, Q. Liu, T. Z. Zhang, D. Li, P. P. Shen, X. L. Dong, Z.-X. Zhao, T. Zhang, D. L. Feng
Chin. Phys. Lett. 2019, 36 (5):
057403
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DOI: 10.1088/0256-307X/36/5/057403
The Majorana zero mode (MZM), which manifests as an exotic neutral excitation in superconductors, is the building block of topological quantum computing. It has recently been found in the vortices of several iron-based superconductors as a zero-bias conductance peak in tunneling spectroscopy. In particular, a clean and robust MZM has been observed in the cores of free vortices in (Li$_{0.84}$Fe$_{0.16}$)OHFeSe. Here using scanning tunneling spectroscopy, we demonstrate that Majorana-induced resonant Andreev reflection occurs between the STM tip and this zero-bias bound state, and consequently, the conductance at zero bias is quantized as $2e^{2}/h$. Our results present a hallmark signature of the MZM in the vortex of an intrinsic topological superconductor, together with its intriguing behavior.
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21 articles
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