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Volume 35 Issue 7
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Multi-Soliton Solutions for the Coupled Fokas–Lenells System via Riemann–Hilbert Approach
Zhou-Zheng Kang, Tie-Cheng Xia, Xi Ma
Chin. Phys. Lett. 2018, 35 (7): 070201 .   DOI: 10.1088/0256-307X/35/7/070201
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We aim to construct multi-soliton solutions for the coupled Fokas–Lenells system which arises as a model for describing the nonlinear pulse propagation in optical fibers. Starting from the spectral analysis of the Lax pair, a Riemann–Hilbert problem is presented. Then in the framework of the Riemann–Hilbert problem corresponding to the reflectionless case, $N$-soliton solutions to the coupled Fokas–Lenells system are derived explicitly.
Period-Doubled Bloch States in a Bose–Einstein Condensate
Bao-Guo Yang, Peng-Ju Tang, Xin-Xin Guo, Xu-Zong Chen, Biao Wu, Xiao-Ji Zhou
Chin. Phys. Lett. 2018, 35 (7): 070301 .   DOI: 10.1088/0256-307X/35/7/070301
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We study systematically the period-doubled Bloch states for a weakly interacting Bose–Einstein condensate in a one-dimensional optical lattice. This kind of state is of form $\psi_k=e^{ikx}\phi_k(x)$, where $\phi_k(x)$ is of a period twice the optical lattice constant. Our numerical results show how these nonlinear period-doubled states grow out of linear period-doubled states at a quarter away from the Brillouin zone center as the repulsive interatomic interaction increases. This is corroborated by our analytical results. We find that all nonlinear period-doubled Bloch states have both Landau instability and dynamical instability.
Compressed Sensing Quantum State Tomography Assisted by Adaptive Design
Qi Yin, Guo-Yong Xiang, Chuan-Feng Li, Guang-Can Guo
Chin. Phys. Lett. 2018, 35 (7): 070302 .   DOI: 10.1088/0256-307X/35/7/070302
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The recently proposed compressed sensing (CS) method sheds light on quantum state tomography of multi-qubit systems with low rank, which greatly reduces the complexity of measurement and computation. However, the restricted isometry property requirement of CS is difficult to be promised or verified in practice, which makes this method probably assign unreasonable results. In regard to this problem, we adopt a two-step procedure and implement an adaptive strategy to update measurement operators based on the measurement results of the first step for CS, which not only serves as a way to verify the estimate but also improves the accuracy of tomography. Our numerical simulations manifest that our adaptive protocol can reduce about half of the infidelity of non-adaptive protocol and is still efficient even when the rank of the state is slightly high, which would greatly benefit multi-qubit state tomography in future experiments.
Nonlinear Excitation and State Transition of Multi-Peak Solitons
Xiang-Shu Liu, Yang Ren, Zhan-Ying Yang, Chong Liu, Wen-Li Yang
Chin. Phys. Lett. 2018, 35 (7): 070501 .   DOI: 10.1088/0256-307X/35/7/070501
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We study the nonlinear excitations in the integrable fifth-order nonlinear Schrödinger equation on a continuous wave background. The excited condition of each localized wave is demonstrated via concise phase diagrams. In particular, the rule of transition between asymmetric and symmetric multi-peak solitons is revealed. It is shown that the initial phase modulation can induce the transition and the transition condition is demonstrated exactly. Interestingly, our result shows that although the multi-peak solitons exhibit structural diversity, both the asymmetric and symmetric states possess an identical asymmetric spectrum structure.
Reconstruction of Intrinsic Thermal Parameters of Methane Hydrate and Thermal Contact Resistance by Freestanding 3$\omega$ Method
Jia Li, Zhao-Liang Wang, Gui-Ce Yao
Chin. Phys. Lett. 2018, 35 (7): 070502 .   DOI: 10.1088/0256-307X/35/7/070502
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It is essential to obtain thermophysical properties of methane hydrate precisely with a freestanding probe for modeling and predicting thermal transport in gas hydrates. A method with a freestanding 3$\omega$ probe is presented to reconstruct the intrinsic thermal conductivity, thermal diffusivity, and thermal contact resistance of methane hydrate. Isolated from the thermal contact resistance, the intrinsic thermal conductivity of methane hydrate decreases between 250 K and 280 K and is 41% larger than the effective value at 253 K. More importantly, when the thermal contact resistance is isolated, the temperature dependence of intrinsic thermal conductivity shows a converse trend with the generally accepted glass-like feature at high temperature. Otherwise, thermal contact resistances measured in the experiment between the freestanding 3$\omega$ probe and the methane hydrate sample are extraordinary large. The freestanding 3$\omega$ method in this work is expected to measure the thermal property of methane hydrate more accurately.
Theoretical Prediction of Diamond Betavoltaic Batteries Performance Using $^{63}$Ni
Yu-Min Liu, Jing-Bin Lu, Xiao-Yi Li, Xu Xu, Rui He, Ren-Zhou Zheng, Guo-Dong Wei
Chin. Phys. Lett. 2018, 35 (7): 072301 .   DOI: 10.1088/0256-307X/35/7/072301
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A diamond p-n junction is used to convert the decay energy of $^{63}$Ni source into electrical energy. The self-absorption effect of the $^{63}$Ni source, the backscatter process and the transport process of beta particles in diamond materials are studied. Then the theoretical maximum of electrical properties and the energy conversion efficiencies of diamond-$^{63}$Ni p-n junction batteries are achieved. Finally, a feasible design of $p^{+}p^{-}n^{+}$ junction battery, which has the maximum output power density of 0.42 $\mu$W/cm$^{2}$ and the optimal device conversion efficiency of 26.8%, is proposed.
Influence of Breaking Waves and Wake Bubbles on Surface-Ship Wake Scattering at Low Grazing Angles
Xiao-Xiao Zhang, Zhen-Sen Wu, Xiang Su
Chin. Phys. Lett. 2018, 35 (7): 074101 .   DOI: 10.1088/0256-307X/35/7/074101
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A surface-ship wake model is proposed for calculating the scattering of ship wake from a nonlinear sea surface at a high sea state. Ship waves are simulated based on the Kelvin wave model by the point-source method. A Creamer II sea surface based on the Elfouhaily sea spectrum is generated, and breaking waves and foam layer effects are taken into account for the background sea scattering at slight, moderate and high wind speeds. Turbulent bubbles scattering from the ship, which is different from wind-driven bubble breaking, is taken into account with a different concentration distribution using a polynomial fitting function combined with measured data. The surface-ship wake scattering is presented for different wind speeds. Numerical simulations show that ship wake scattering results will be higher when wake bubbles are taken into account. The ship beam is a key parameter that influences the width of the turbulent wake, and results in different scattering characteristics on the scattering image. The wind-induced surface in the presence of breaking waves and whitecaps results in scattering enhancement. This will cause the ship wake signal to be submerged in the back-ground of sea noise, leading to false alarms.
Radiation Effects Due to 3MeV Proton Irradiations on Back-Side Illuminated CMOS Image Sensors
Xiang Zhang, Yu-Dong Li, Lin Wen, Dong Zhou, Jie Feng, Lin-Dong Ma, Tian-Hui Wang, Yu-Long Cai, Zhi-Ming Wang, Qi Guo
Chin. Phys. Lett. 2018, 35 (7): 074201 .   DOI: 10.1088/0256-307X/35/7/074201
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Benefitting from the higher quantum efficiency and sensitivity compared with the front-side illumination (FSI) CMOS image sensors (CISs), backside illumination (BSI) CMOS image sensors tend to replace CCDs and FSI CISs for space applications. However, the radiation damage effects and mechanisms of BSI CISs in the radiation environment are not well understood. We provide radiation effects due to 3 MeV proton irradiations of BSI CISs dedicated to imaging by the analyses of mean dark current increase, dark current nonuniformity and full well capacity in pixel arrays and isolated photodiodes. Additionally, the present annealing certifies the radiation-induced defects, which are responsible for the parameter degradations in BSI CISs.
Improvement of Stability of $^{40}$Ca$^{+}$ Optical Clock with State Preparation
Meng-Yan Zeng, Yao Huang, Hu Shao, Miao Wang, Hua-Qing Zhang, Bao-Lin Zhang, Hua Guan, Ke-Lin Gao
Chin. Phys. Lett. 2018, 35 (7): 074202 .   DOI: 10.1088/0256-307X/35/7/074202
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Stability is one of most important performances of an atomic clock. Here we describe our recent work on improving the stability of our $^{40}$Ca$^{+}$ optical clock. State preparation is adopted to transfer the ion to the ground-state magnetic sublevel of the clock transition, after the quenching laser transfers the ion to the ground state at each cycle. Using this method, the stability for $^{40}$Ca$^{+}$ optical clock is improved to about $6.3\times 10^{-15}/\sqrt\tau$. Compared with $1.0\times 10^{-14}/\sqrt \tau$ in previous work, the averaging time is decreased to reach a given level of statistical uncertainty in a clock comparison.
Variational Analysis of High-Frequency Effect on Moving Electromagnetic Interface
Kang-Bo Tan, Hong-Min Lu, Qiao Guan, Guang-Shuo Zhang, Chong-Chong Chen
Chin. Phys. Lett. 2018, 35 (7): 074203 .   DOI: 10.1088/0256-307X/35/7/074203
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Based on Fermat's principle and the special relativity, the transmission of high-frequency electromagnetics is unified by variational formulation on the moving interface. Applying the theoretical model, we investigate the detailed practices of transmission of high-frequency electromagnetic under relativistic conditions. The deduced results illustrate that the effective estimation of the super high-speed effect on a moving interface supports the valuable frame of reference in controlling precision. The results also show that the theoretical model has potential applications in electromagnetically controlled precision in the quantum information, ray sensor, controllable environment, etc.
Field Tunable Polaritonic Band Gaps in Fibonacci Piezoelectric Superlattices
Zheng-Hua Tang, Zheng-Sheng Jiang, Chun-Zhi Jiang, Da-Jun Lei, Jian-Quan Huang, Feng Qiu, Hai-Ming Deng, Min Yao, Xiao-Yi Huang
Chin. Phys. Lett. 2018, 35 (7): 074204 .   DOI: 10.1088/0256-307X/35/7/074204
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The Fibonacci piezoelectric superlattices (FPSs) with an external dc electric field is presented, in which the dc electric field can tune the bandwidth of polaritonic band gaps (PBGs) continuously and reversibly via the electro-optic effect. The absolute bandwidths of two major PBGs of the FPSs around $\omega=7.5$ GHz and $\omega=12.5$ GHz can be broadened from 0.022 GHz to 0.74 GHz and from 0.02 GHz to 0.82 GHz with the dc electric field increasing from 0 to $1.342\times10^{6}$ V/m, respectively. The corresponding relative bandwidths of the two major PBGs are widened from $0.28\%$ to $9.2\%$ and from $0.18\%$ to $6.35\%$, respectively. The general mechanism for the bandwidth tunability is that the coupling strength between the lattice vibration and electromagnetic waves is capable of being altered by the dc electric field via the electro-optic effect. Thus the properties can be applied to construct microwave switchings or field tunable bulk acoustic filters.
Propagation and Damping of Two-Fluid Magnetohydrodynamic Waves in Stratified Solar Atmosphere
Yong-Jian Jin, Hui-Nan Zheng, Zhen-Peng Su
Chin. Phys. Lett. 2018, 35 (7): 075201 .   DOI: 10.1088/0256-307X/35/7/075201
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An extreme ultra-violet (EUV) wave is characterized as a bright pulse that has emanated from the solar eruption source and can propagate globally in the solar corona. According to one leading theory, the EUV wave is a fast magnetoacoustic wave, as the coronal counterpart of the Moreton wave in the chromosphere. However, previous observations have shown that the EUV wave differs significantly from the Moreton wave in both velocity and lifetime. To reconcile these differences, here we analyze the wave characteristics of a two-fluid MHD model in the stratified solar atmosphere with a height-dependent ionization rate. It is found that the collision between neutral and ionized fluids is able to attenuate the wave amplitude, while causing a slight change in its propagation velocity. Because the chromosphere has the lower ionization rate and the stronger magnetic fields than the corona, the velocity of the Moreton wave is much higher than that of the EUV wave. In contrast to the Moreton waves damped strongly by the collision between neutral and ionized fluids, the EUV wave in the fully ionized corona is able to propagate globally on a time scale of several hours. Our results support the previous theory that fast magnetoacoustic waves account for both EUV and Moreteon waves in the different layers of the solar atmosphere.
Dynamics of Ring-to-Volume Discharge Transition in $H$ Mode in Inductively Coupled Plasma Torches at Atmospheric Pressure
Qi-Jia Guo, Guo-Hua Ni, Lin Li, Qi-Fu Lin, Yan-Jun Zhao, Si-Yuan Sui, Hong-Bing Xie, Wen-Xue Duan, Yue-Dong Meng
Chin. Phys. Lett. 2018, 35 (7): 075202 .   DOI: 10.1088/0256-307X/35/7/075202
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The transition process in ring-to-volume discharge in $H$ mode in inductively coupled plasma torches at atmospheric pressure is investigated by analyzing the time resolved image taken by a high speed camera. The effects of input power, plasma working gas flow rate, and its composition on the transition dynamics are also discussed. The results show that the discharge plasma has experienced ring discharge, and the development stage diffused from the boundary to the center in the confinement tube, and steady volume discharge after entering the $H$ mode. Increasing input power, sheath gas flow rate and hydrogen contents in plasma working gas are all able to lessen the time consumed in the transition process in ring-to-volume discharge.
An Efficiency Enhanced Graphene/n-Si Schottky Junction for Solar Cells
Gang Li, Hong-Wei Cheng, Li-Fang Guo, Kai-Ying Wang, Zai-Jun Cheng
Chin. Phys. Lett. 2018, 35 (7): 076801 .   DOI: 10.1088/0256-307X/35/7/076801
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A novel and facile oxidation-induced self-doping process of graphene-silicon Schottky junction by nitric acid (HNO$_{3}$) vapor is reported. The HNO$_{3}$ oxidation process makes graphene p-type self-doped, and leads to a higher built-in potential and conductivity to enhance charge transfer and to suppress charge carrier recombination at the graphene-silicon Schottky junction. After the HNO$_{3}$ oxidation process, the open-circuit voltage is increased from the initial value of 0.36 V to the maximum value of 0.47 V, the short-circuit current is greatly increased from 0.80 $\mu$A to 7.71 $\mu$A, and the ideality factor is optimized from 4.4 to 1.0. The enhancement of the performance of graphene-Si solar cells may be due to oxidation-induced p-type self-doping of graphene-Si junctions.
Quantum Anomalous Hall Multilayers Grown by Molecular Beam Epitaxy
Gaoyuan Jiang, Yang Feng, Weixiong Wu, Shaorui Li, Yunhe Bai, Yaoxin Li, Qinghua Zhang, Lin Gu, Xiao Feng, Ding Zhang, Canli Song, Lili Wang, Wei Li, Xu-Cun Ma, Qi-Kun Xue, Yayu Wang, Ke He
Chin. Phys. Lett. 2018, 35 (7): 076802 .   DOI: 10.1088/0256-307X/35/7/076802
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Quantum anomalous Hall (QAH) effect is a quantum Hall effect that occurs without the need of external magnetic field. A system composed of multiple parallel QAH layers is an effective high Chern number QAH insulator and the key to the applications of the dissipationless chiral edge channels in low energy consumption electronics. Such a QAH multilayer can also be engineered into other exotic topological phases such as a magnetic Weyl semimetal with only one pair of Weyl points. This work reports the first experimental realization of QAH multilayers in the superlattices composed of magnetically doped (Bi,Sb)$_{2}$Te$_{3}$ topological insulator and CdSe normal insulator layers grown by molecular beam epitaxy. The obtained multilayer samples show quantized Hall resistance $h/Ne^{2}$, where $h$ is Planck's constant, $e$ is the elementary charge and $N$ is the number of the magnetic topological insulator layers, resembling a high Chern number QAH insulator. The QAH multilayers provide an excellent platform to study various topological states of matter.
Topological Invariants in Terms of Green's Function for the Interacting Kitaev Chain
Zhidan Li, Qiang Han
Chin. Phys. Lett. 2018, 35 (7): 077101 .   DOI: 10.1088/0256-307X/35/7/077101
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A one-dimensional closed interacting Kitaev chain and the dimerized version are studied. The topological invariants in terms of Green's function are calculated by the density matrix renormalization group method and the exact diagonalization method. For the interacting Kitaev chain, we point out that the calculation of the topological invariant in the charge density wave phase must consider the dimerized configuration of the ground states. The variation of the topological invariant is attributed to the poles of eigenvalues of the zero-frequency Green functions. For the interacting dimerized Kitaev chain, we show that the topological invariant defined by Green's functions can distinguish more topological nonequivalent phases than the fermion parity.
Band Structures of Ultrathin Bi(110) Films on Black Phosphorus Substrates Using Angle-Resolved Photoemission Spectroscopy
Sailong Ju, Maokun Wu, Hao Yang, Naizhou Wang, Yingying Zhang, Peng Wu, Pengdong Wang, Bo Zhang, Kejun Mu, Yaoyi Li, Dandan Guan, Dong Qian, Feng Lu, Dayong Liu, Wei-Hua Wang, Xianhui Chen, Zhe Sun
Chin. Phys. Lett. 2018, 35 (7): 077102 .   DOI: 10.1088/0256-307X/35/7/077102
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The band structures of two-monolayer Bi(110) films on black phosphorus substrates are studied using angle-resolved photoemission spectroscopy. Within the band gap of bulk black phosphorus, the electronic states near the Fermi level are dominated by the Bi(110) film. The band dispersions revealed by our data suggest that the orientation of the Bi(110) film is aligned with the black phosphorus substrate. The electronic structures of the Bi(110) film strongly deviate from the band calculations of the free-standing Bi(110) film, suggesting that the substrate can significantly affect the electronic states in the Bi(110) film. Our data show that there are no non-trivial electronic states in Bi(110) films grown on black phosphorus substrates.
Influence of Triangle Structure Defect on the Carrier Lifetime of the 4H-SiC Ultra-Thick Epilayer
Ying-Xi Niu, Xiao-Yan Tang, Ren-Xu Jia, Ling Sang, Ji-Chao Hu, Fei Yang, Jun-Min Wu, Yan Pan, Yu-Ming Zhang
Chin. Phys. Lett. 2018, 35 (7): 077103 .   DOI: 10.1088/0256-307X/35/7/077103
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Effect of triangle structure defects in a 180-μm-thick as-grown n-type 4H-SiC homoepitaxial layer on the carrier lifetime is quantitatively analyzed, which is grown by a horizontal hot-wall chemical vapor deposition reactor. By microwave photoconductivity decay lifetime measurements and photoluminescence measurements, the results show that the average carrier lifetime of as-grown epilayer across the whole wafer is 2.59 μs, while it is no more than 1.34 μs near a triangle defect (TD). The scanning transmission electron microscope results show that the triangle structure defects have originated from 3C-SiC polytype and various types of as-grown stacking faults. Compared with the as-grown stacking faults, the 3C-SiC polytype has a great impact on the lifetime. The reduction of TD is essential to increasing the carrier lifetime of the as-grown thick epilayer.
Two Gaps in Semiconducting EuSbTe$_3$ Studied by Angle-Resolved Photoemission Spectroscopy
Cong-Cong Fan, Ji-Shan Liu, Kai-Li Zhang, Wan-Ling Liu, Xiang-Le Lu, Zheng-Tai Liu, Dong Wu, Zhong-Hao Liu, Da-Wei Shen, Li-Xing You
Chin. Phys. Lett. 2018, 35 (7): 077104 .   DOI: 10.1088/0256-307X/35/7/077104
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Using angle-resolved photoemission spectroscopy, we study the low-energy electronic structure of a layered ternary telluride EuSbTe$_3$ semiconductor. It is found that the photoemission constant energy contours can be well described by the simple two-parameter ($t_{\rm perp}$ and $t_{\rm para}$) tight-binding model based on the Te orbitals in square-net planes of EuSbTe$_3$, suggesting its Te 5$p$ orbitals dominated low-lying electronic structure, which is reminiscent of other rare-earth tritellurides. However, a possible charge-density-wave gap of 80 meV is found to persist in 300 K, which renders the unexpected semiconducting properties in EuSbTe$_3$. Moreover, we reveal an extra band gap occurring around 200 meV below the Fermi level at low temperatures, which can be attributed to the interaction between the main and folded bands due to lattice scatterings. Our findings provide the first comprehensive understanding of the electronic structure of layered ternary tellurides, which lays the basis for future research on these compounds.
Transport Studies on GaAs/AlGaAs Two-Dimensional Electron Systems Modulated by Triangular Array of Antidots
Chu-Hong Yang, Shu-Yu Zheng, Jie Fan, Xiu-Nian Jing, Zhong-Qing Ji, Guang-Tong Liu, Chang-Li Yang, Li Lu
Chin. Phys. Lett. 2018, 35 (7): 077301 .   DOI: 10.1088/0256-307X/35/7/077301
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Triangular antidot lattices of various periods and aspect ratios are fabricated on high mobility GaAs/AlGaAs two-dimensional electron systems (2DESs), and are characterized by magneto-transport measurements at low temperatures down to 300 mK. Commensurability peaks are generally observed in the magneto-resistivity $\rho_{xx}$, and remarkable similarity between $d\rho_{xy}/dB$ and $\rho_{xx}$ is found. In samples of relatively large aspect ratio $d/a$, the Aharonov–Bohm-type oscillations are clearly observed in both $\rho_{xx}$ and $\rho_{xy}$, as well as the quenching of the Hall resistivity $\rho_{xy}$ in the vicinity of $B=0$. These observations evince the good quality of our samples, and attest to the adequate preparation for fabricating antidot lattices of a reduced period to realize artificial graphene from GaAs/AlGaAs 2DESs.
Improvements of Interfacial and Electrical Properties for Ge MOS Capacitor with LaTaON Gate Dielectric by Optimizing Ta Content
Bin-Xu, Jing-Ping Xu, Lu Liu, Yong Su
Chin. Phys. Lett. 2018, 35 (7): 077302 .   DOI: 10.1088/0256-307X/35/7/077302
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The interfacial and electrical properties of high-$k$ LaTaON gate dielectric Ge metal-oxide-semiconductor (MOS) capacitors with different tantalum (Ta) contents are investigated. Experimental results show that the Ge MOS capacitors with a Ta content of $\sim$30% exhibit the best interfacial and electrical properties, including low interface-state density $(7.6\times10^{11}$ cm$^{-2}$ eV$^{-1}$), small gate-leakage current $(8.32\times10^{-5}$ A/cm$^{2}$) and large equivalent permittivity (22.46). The x-ray photoelectron spectroscopy results confirm that the least GeO$_{x}$ is formed at the Ge surface for the sample with a Ta content of $\sim$30% due to the effective blocking role of Ta against O diffusion and the greatly improved hygroscopicity of LaON.
Observation of Weak Anti-Localization and Electron-Electron Interaction on Few-Layer 1T$'$-MoTe$_2$ Thin Films
Qin Wang, Peng Yu, Xiangwei Huang, Jie Fan, Xiunian Jing, Zhongqing Ji, Zheng Liu, Guangtong Liu, Changli Yang, Li Lu
Chin. Phys. Lett. 2018, 35 (7): 077303 .   DOI: 10.1088/0256-307X/35/7/077303
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Electronic transports of few-layer 1T$'$-MoTe$_2$ films are measured at temperatures down to 0.26 K. The low-temperature conductivity exhibits logarithmic temperature dependence and negative magneto response. The negative magnetoconductivity can be well fitted by the two-dimensional weak anti-localization theory taking a single channel of electrons into account, with the parameters $\alpha\approx -0.5$ and $l_{\phi} \propto T^{-0.5}$. The logarithmic temperature dependence has a positive slope $\kappa\approx0.75$, indicating the dominance of electron-electron interaction over the weak anti-localization effect, with an apparently negative Coulomb screening factor $F$ that demands future work for clarification.
Electrical Conductivity of a Single Electro-deposited CoZn Nanowire
Hong-Jun Wang, Yuan-Yuan Zhu, Jing Zhou, Yong Liu
Chin. Phys. Lett. 2018, 35 (7): 077304 .   DOI: 10.1088/0256-307X/35/7/077304
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CoZn nanowires are fabricated by the electrodeposition method at constant voltage mode with porous anodic aluminum oxide as templates. Scanning electron microscope and transmission electron microscope images show that the CoZn nanowires have a rather smooth surface. The nanowires have an average diameter of 50 nm, which coincides with the diameter of the used templates. The x-ray diffraction pattern reveals the polycrystalline structure of the CoZn nanowires. The electrical conductivity of a single CoZn nanowire is studied. The metallic behavior is observed at temperatures from 230 K to 30 K. Moreover, an abnormal behavior appears around 30 K. The resistance shows the slight upturn phenomenon below 30 K down to 2 K, which is due to the major conduction role of the oxidation layer on the surface of the CoZn nanowire.
Possible Evidence for Spin-Transfer Torque Induced by Spin-Triplet Supercurrents
Lai-Lai Li, Yue-Lei Zhao, Xi-Xiang Zhang, Young Sun
Chin. Phys. Lett. 2018, 35 (7): 077401 .   DOI: 10.1088/0256-307X/35/7/077401
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The mutual interplay between superconductivity and magnetism in superconductor/ferromagnet heterostructures may give rise to unusual proximity effects beyond current knowledge. Especially, spin-triplet Cooper pairs could be created at carefully engineered superconductor/ferromagnet interfaces. Here we report a giant proximity effect on spin dynamics in superconductor/ferromagnet/superconductor Josephson junctions. Below the superconducting transition temperature $T_{\rm C}$, the ferromagnetic resonance field at X-band ($\sim$9.0 GHz) shifts rapidly to a lower field with decreasing temperature. In strong contrast, this phenomenon is absent in ferromagnet/superconductor bilayers and superconductor/insulator/ferromagnet/superconductor multilayers. Such an intriguing phenomenon can not be interpreted by the conventional Meissner effect. Instead, we propose that the strong influence on spin dynamics could be due to spin-transfer torque associated with spin-triplet supercurrents in ferromagnetic Josephson junctions with precessing magnetization.
Magnetoresistance Detection of Vortex Domain in a Notched FeNi Nanowire
Guang-Tian Hai, Wen-Xiu Zhao, Jia-Shu Chen, Zheng-Hua Li, Jia-Liang He
Chin. Phys. Lett. 2018, 35 (7): 077501 .   DOI: 10.1088/0256-307X/35/7/077501
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Revealing the physical nature of vortex wall (VW) behavior in magnetic nanostructures has been of great importance for future device concepts. Here we introduce the superior properties of VW in a notched FeNi nanowire under the action of an electronic current. The pinning-dependent VW propagation is demonstrated by a successive in-field magnetic force microscopy, an anisotropic magnetoresistance measurement, as well as micromagnetics. Based on the developed method, the propagation of VW can be effectively captured by monitoring the change of magnetoresistance in the FeNi nanowire, which sheds light on the development of future spin-based devices.
Hybridization Induced Competitive Scanning Tunneling Interference Process into a Heavy Fermion System
Fu-Bin Yang
Chin. Phys. Lett. 2018, 35 (7): 077502 .   DOI: 10.1088/0256-307X/35/7/077502
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We theoretically present the results for a scanning interference tunneling process between a metallic tip and a heavy fermion system. The density of states (DOS) and the differential conductance at zero temperature under different $c$–$f$ band hybridizations, as well as the interference Fano ratio strength in the heavy fermion system, are calculated. It is found that the hybridization strength gives rise to the splitting effect in the DOS around the Fermi energy. Also the interference Fano ratio strength makes the differential conductance characteristics strongly asymmetric.
Magnetic and Transport Properties of the Kondo Lattice Compound YbPtAs
Hui Liang, Shuai Zhang, Yu-Jia Long, Jun-Bao He, Jing Li, Xin-Min Wang, Zhi-An Ren, Gen-Fu Chen
Chin. Phys. Lett. 2018, 35 (7): 077503 .   DOI: 10.1088/0256-307X/35/7/077503
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We report the electrical resistivity, magnetic susceptibility, and heat capacity studies on a new intermetallic compound YbPtAs, which crystallizes in a modified AlB$_2$ type structure. The Yb ions in YbPtAs are in a trivalent state and order antiferromagnetically around Néel temperatures $T_{\rm N1}=6.5$ K and $T_{\rm N2}=2.2$ K, respectively, deduced both from the magnetic susceptibility $\chi(T)$ and heat capacity $C(T)$ measurements. The magnetic contribution in resistivity, $\rho_{\rm m}(T)$, exhibits a broad maximum at around 100 K and a logarithmic temperature dependence in the high-temperature region, indicative of the presence of the Kondo effect in YbPtAs.
A Reflective Inorganic All-Thin-Film Flexible Electrochromic Device with a Seven-Layer Structure
Chao Zhou, Hui Zhou, Hua-Ping Zuo, Kai-Feng Zhang, Hu Wang, Yu-Qing Xiong
Chin. Phys. Lett. 2018, 35 (7): 077801 .   DOI: 10.1088/0256-307X/35/7/077801
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A reflective electrochromic device is fabricated on a 10 cm$\times$10 cm flexible PI/Al substrate using magnetron sputtering. The device has a complementary all-thin-film structure and consists of seven layers. Indium tin oxide (ITO) acts as a transparent electrode deposited on the top, meanwhile, an aluminum (Al) film is adopted as an inter-counter bottom electrode and provides high reflectance. Tungsten oxide (WO$_{3}$) is used as the main electrochromic layer and nickel oxide (NiO) acts as the complementary electrochromic layer. Lithium niobate (LiNbO$_{3}$) is applied as a Li$^{+}$ ion conductor layer. Especially, in the seven-layer structure, two tantalum oxides (Ta$_{2}$O$_{5}$) are added as transition layers to prevent Li$^{+}$ escaping from LiNbO$_{3}$ when the potential is not applied on the device. When the device is in an electrochromic process, both Ta$_{2}$O$_{5}$ provide excellent conductivity for Li$^{+}$ ions and act as the dielectric of electrons. The complementary device with structure Al/NiO/Ta$_{2}$O$_{5}$/LiNbO$_{3}$/Ta$_{2}$O$_{5}$/WO$_{3}$/ITO exhibits good optical properties, and the reflectance modulation reaches up to 55% measured by a spectrophotometer in the range of 400–1600 nm. The cyclic stability of the electrochromic device is investigated. The results indicate that the charge density involved in the electrochromic process decreases and the electrochromic response time increases with the cycle number because of the Li$^{+}$ insertion in WO$_{3}$.
Growth and Characterization of the Laterally Enlarged Single Crystal Diamond Grown by Microwave Plasma Chemical Vapor Deposition
Ze-Yang Ren, Jin-Feng Zhang, Jin-Cheng Zhang, Sheng-Rui Xu, Chun-Fu Zhang, Kai Su, Yao Li, Yue Hao
Chin. Phys. Lett. 2018, 35 (7): 078101 .   DOI: 10.1088/0256-307X/35/7/078101
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Laterally enlarged single crystal diamond is grown on (001) diamond substrates by microwave plasma chemical vapor deposition. Based on the largest side-to-side width of the seed of 7.5 mm, we achieve the as-grown epilayer with the width of about 10 mm between the same two sides. The luminescence difference between the broadened part of the single crystal diamond and the vertically epitaxial part is investigated by characterizing the vertical cross section of the sample, and the possible growth mechanism is suggested. Vertical epitaxy on the top (001) surface and lateral growth on the side surfaces occur simultaneously, and thus the growth fronts along the two directions adjoin and form a coalescence zone extending from the edge of the substrate towards the edge of the expanded single crystal diamond top surface. The luminescence intensity of the nitrogen-vacancy center is relatively high in the coalescence zone and a laterally grown part right below, which are attributed mainly to the higher growth rate. However, stress change and crystal quality change are negligible near the coalescence zone.
Wavelength Extended InGaAsBi Detectors with Temperature-Insensitive Cutoff Wavelength
Ben Du, Yi Gu, Yong-Gang Zhang, Xing-You Chen, Ying-Jie Ma, Yan-Hui Shi, Jian Zhang
Chin. Phys. Lett. 2018, 35 (7): 078501 .   DOI: 10.1088/0256-307X/35/7/078501
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We demonstrate a wavelength extended InGaAsBi short-wave infrared photodetector on an InP substrate with the 50% cutoff wavelength up to 2.63 μm at room temperature. The moderate growth temperature is applied to balance the Bi incorporation and material quality. Photoluminescence and x-ray diffraction reciprocal space mapping measurements reveal the contents of bismuth and indium in InGaAsBi to be about 2.7% and 76%, respectively. The InGaAsBi detector shows the temperature-insensitive cutoff wavelength with a low coefficient of about 0.96 nm/K. The demonstration indicates the InP-based InGaAsBi material is a promising candidate for wavelength extended short-wave infrared detectors working.
Total Ionizing Dose Effects of 55-nm Silicon-Oxide-Nitride-Oxide-Silicon Charge Trapping Memory in Pulse and DC Modes
Mei Li, Jin-Shun Bi, Yan-Nan Xu, Bo Li, Kai Xi, Hai-Bin Wang, Jing-Liu, Jin-Li, Lan-Long Ji, Li Luo, Ming Liu
Chin. Phys. Lett. 2018, 35 (7): 078502 .   DOI: 10.1088/0256-307X/35/7/078502
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The $^{60}$Co-$\gamma$ ray total ionizing dose radiation responses of 55-nm silicon-oxide-nitride-oxide-silicon (SONOS) memory cells in pulse mode (programmed/erased with pulse voltage) and dc mode (programmed/erased with direct voltage sweeping) are investigated. The threshold voltage and off-state current of memory cells before and after radiation are measured. The experimental results show that the memory cells in pulse mode have a better radiation-hard capability. The normalized memory window still remains at 60% for cells in dc mode and 76% for cells in pulse mode after 300 krad(Si) radiation. The charge loss process physical mechanisms of programmed SONOS devices during radiation are analyzed.
Photoelectric Property Improvement of 1.0-eV GaInNAs and Applications in Lattice-Matched Five-Junction Solar Cells
Bing-zhen Chen, Yang Zhang, Qing Wang, Zhi-yong Wang
Chin. Phys. Lett. 2018, 35 (7): 078801 .   DOI: 10.1088/0256-307X/35/7/078801
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GaInNAs with bandgap 1.0 eV is a promising material for multi-junction solar cell applications. However, the poor quality of GaInNAs grown by metalorganic chemical vapor deposition hinders its device performance. Here to reap the benefits of 1.0-eV sub-cell, we focus on the optimization of annealing temperature and growth ambient of GaInNAs. The GaInNAs sub-cell exhibits a concentration reduction of shallow level defects when it is annealed at 700 $\,^{\circ}\!$C for 20 min. As compared with the growth case using a hydrogen ambient, the N incorporation efficiency of GaInNAs can be enhanced during the growth in an N$_{2}$ ambient. Furthermore, background carbon concentration is observed to reduce in the as-grown GaInNAs epilayer. A GaInNAs sub-cell with 82% peak external quantum efficiency is obtained in a dual-junction GaInNAs/Ge solar cell. Finally, a monolithic AlGaInP/AlGaInAs/GaInAs/GaInNAs/Ge five-junction solar cell is grown for space application. The fabricated device shows a conversion efficiency of 31.09% and a short-circuit current density of 11.81 mA/cm$^{2}$ under 1 sun AM 0 illumination.
Effect of Tidal Torques on Rotational Mixing in Close Binaries
Zhi Li, Han-Feng Song, Wei-Guo Peng
Chin. Phys. Lett. 2018, 35 (7): 079701 .   DOI: 10.1088/0256-307X/35/7/079701
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The effect of tidal torques on rotational mixing in close binaries is investigated. It is found that spin angular momentum can attain a high value due to a strong tidal torque. Nitrogen and helium enrichment occurs early in the binary system that is triggered by tides. The stellar radius can reach a high value in the single star model with high initial velocities at the early stage of the evolution, but efficient rotational mixing can inhibit stellar expanding at the subsequent evolution. Central compactness is increased by the centrifugal force at the early stage of evolution but is reduced by rotational mixing induced by strong tides. The binary models with weak tides have high values of central temperature and stellar radius. Rotational mixing in single stars can slow down the shrinkage of convective cores, while convective cores can be expanded by strong tides in the binary system. Efficient rotational mixing induced by tides can cause the star to evolve towards high temperature and luminosity.
33 articles