作者机构：
Hunan Key Laboratory of Nanophotonics and Devices, School of Physics, Central South University;School of Physics and Electronic Science, Changsha University of Science and Technology
通讯机构：
[Ziyuan Li] M;[Xiaoming Yuan] H;MoE Key Laboratory of Photoelectronic Imaging Technology and System, School of Optics and Photonics, Beijing Institute of Technology, Beijing 100081, People's Republic of China<&wdkj&>Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra ACT 2601, Australia<&wdkj&>Hunan Key Laboratory of Super Microstructure and Ultrafast Process, School of Physics and Electronic, Central South University, 932 South Lushan Road, Changsha, Hunan 410083, People's Republic of China
摘要：
Polarization-sensitive infrared photodetectors are widely needed to distinguish an object from its surrounding environment. Polarization-sensitive detection can be realized by using semiconductors with anisotropic geometry or anisotropic crystal arrangement, such as semiconductor nanowires and two-dimensional (2D) materials. However, these photodetectors show drawbacks in low light absorption, weak polarization sensitivity and stability issues. Here, we designed 2D InAs nanosheet based arrays that are highly suitable for polarization-sensitive infrared photodetection. By using the finite element method (FEM) based on COMSOL Multiphysics, we optimized the geometry of single free-standing InAs nanosheets, obtaining dichroic ratio up to 127 (average) in the wavelength range of 2-3 mu m by reducing the thickness and increasing the height. Extending this to a nanosheet array with an optimized geometry, an enhancement of the absorption intensity from 45% (for a single nanosheet) to over 67% with a dichroic ratio exceeding 50 in the wavelength range of 2-3 mu m can be achieved. Moreover, these unique light absorption properties are tolerant to incident angles up to 30 degrees. The design of such nanosheet array provides a new route for the development of high-performance infrared photodetectors for polarization photodetection.
摘要：
Ferroelectric materials have received great attention in the field of data storage, benefiting from their exotic transport properties. Among these materials, the two-dimensional (2D) In(2)Se(3) has been of particular interest because of its ability to exhibit both in-plane and out-of-plane ferroelectricity. In this article, we realized the molecular beam epitaxial (MBE) growth of β-In(2)Se(3) films on bilayer graphene (BLG) substrates with precisely controlled thickness. Combining in situ scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES) measurements, we found that the four-monolayer β-In(2)Se(3) is a semiconductor with a (9 × 1) reconstructed superlattice. In contrast, the monolayer β-In(2)Se(3)/BLG heterostructure does not show any surface reconstruction due to the interfacial interaction and moiré superlattice, which instead results in a folding Dirac cone at the center of the Brillouin zone. In addition, we found that the band gap of In(2)Se(3) film decreases after potassium doping on its surface, and the valence band maximum also shifts in momentum after surface potassium doping. The successful growth of high-quality β-In(2)Se(3) thin films would be a new platform for studying the 2D ferroelectric heterostructures and devices. The experimental results on the surface reconstruction and band structures also provide important information on the quantum confinement and interfacial effects in the epitaxial β-In(2)Se(3) films.
作者机构：
[Ji, Yan; Guo, Jin-mei; Zhu, Hua-li; Lu, Chao-cao; Zhu, Min-dan] Changsha Univ Sci & Technol, Sch Phys & Elect Sci, Changsha 410114, Peoples R China.;[Zhu, Hua-li] Changsha Univ Sci & Technol, Coll Energy & Power Engn, Changsha 410114, Peoples R China.;[Tan, Xin-xin; Hu, Jin] Basf Shanshan Battery Mat Ningxiang Co Ltd, Changsha 410605, Peoples R China.;[Chen, Zhao-yong] Changsha Univ Sci & Technol, Sch Mat Sci & Engn, Changsha 410114, Peoples R China.;[Chen, Zhao-yong] Changsha Univ Sci & Technol, Inst New Energy & Power Battery, Changsha 410114, Peoples R China.
通讯机构：
[Hua-li Zhu] S;School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha, China<&wdkj&>College of Energy and Power Engineering, Changsha University of Science and Technology, Changsha, China
关键词：
Lithium-ion battery;LiNi0.8Co0.1Mn0.1O2;Conductive oxide;Coating;Cathode material
摘要：
High-nickel cathode material has high specific capacity, but the rapid capacity decay restricts its application. Hereby, three conductive oxides including nano-antimony tin oxide (Sb2SnO5, ATO), zinc stannate (Zn2SnO4, ZTO), and antimony-doped zinc stannate (Sb-doped ZTO, AZTO) with high mobility and low resistivity were used as coating materials separately to improve the rate capability and cycling stability of LiNi0.8Co0.1Mn0.1O2 (NCM811). The conductive oxide was uniformly coated on the surface of NCM811 with the thickness of about 4 nm. The AZTO-coated NCM811 shows the superior rate capability with the initial discharge capacities of 201.35, 197.86, 190.80, and 182.31 mAh g(-1) at 0.1, 0.2, 0.5, and 1 C, respectively. The ZTO-coated NCM811 has the best cycling stability with the capacity retention of 85.93% after 100 cycles, while that of the pristine NCM811 is 66.75%. The conductive oxides improve the electronic/ionic conductivity and block the reaction between cathode material and electrolyte, reduce the electrochemical impedance and the side reaction, and further increase the rate capability and the reversibility of the materials.
摘要：
Whistler mode wave is a crucial emission which can significantly affect the electron dynamics in the magnetosphere. The nonlinear three-wave interaction between whistler mode waves has been frequently observed, while the four-wave interaction between these waves is seldom reported. Here, we present two multiband whistler mode wave events by Van Allen Probes, in which the relatively weak wave bands occur exactly corresponding to the strong wave bands. We find that the frequencies of the weak and strong bands satisfy the frequency matching conditions of the four-wave interaction, and the wave normal angles of the weak bands are almost within the possible ranges calculated from the wave vector matching conditions. Additionally, the cross-correlation coefficients between the amplitudes of the weak bands and that of strong bands approach 0.80. These results indicate that the weak bands are very likely to be produced by the four-wave interaction between whistler mode waves. Similar to the three-wave interaction, the four-wave interaction can extend the frequency of whistler mode waves from close to 0.5fce to a wider range in both the lower (0.26fce) and upper (0.78fce) bands, and thus potentially play an important role in the electron dynamics.
Two multiband whistler mode wave events are reported in which relatively weak wave bands occur exactly corresponding to the strong bands
Frequency and wave vector matching conditions of the four-wave interaction are found to be satiated in both events
Four-wave interactions between whistler mode waves can cause the frequency broadening, potentially affecting the electron dynamics
摘要：
Negative magnetoresistance (NMR) is a marked feature of Dirac semimetals, and may be caused by multiple mechanisms, such as the chiral anomaly, the Zeeman energy, the quantum interference effect, and the orbital moment. Recently, an experiment on Dirac semimetal Cd3As2 thin films revealed a new NMR feature that depends strongly on the thickness of the sample [T. Schumann et al., Phys. Rev. B 95, 241113(R) (2017)]. Here, we introduce a mechanism of inducing NMR via the presence of the Van Hove singularity (VHS) in the density of states. A theoretical fitting of the experimental data on magnetoconductivity and magnetoresistance shows good agreement, indicating that the observed NMR in thin films of Cd3As2 can be attributed to the VHS. This work provides insights into the underlying Dirac semimetals.
关键词：
density functional theory;two-dimensional magentism;Dzyaloshinskii-Moriya interaction
摘要：
The magnetic heterostructures provide flexible ways to realize particular magnetic properties that possess both scientific and practical significance. Here, by first principles calculation, we predict strong Dzyaloshinskii-Moriya interactions (DMIs) by constructing CrI3/Metal vdW heterostructures. The underlaying mechanisms are ascribed to the large spin-orbital coupling (SOC) of the I atom and the structural distortion in CrI3 layer caused by interlayer interaction. This is different from the traditional way that deposit magnetic films on substrate to generate DMI, wherein DMI is dominated by interlayer hybridization and large SOC of substrates. In addition, both Heisenberg exchange and magnetic anisotropy are modulated dramatically, such as Heisenberg exchange is nearly doubled on Au(111), and the out-of-plane magnetism is enhanced by 88% on Ir(111). Our work may provide a experimentally accessible strategy to induce DMI in layered magnetic materials, which will be helpful to the design of spintronics devices.
摘要：
Electrostatic electron cyclotron harmonic (ECH) waves which can efficiently produce scattering loss of electrons, are frequently observed in the first band. Here we present new results on the global occurrence of higher-band ECH waves in the radiation belts from Van Allen Probes data. We develop a novel noise reduction algorithm which can be widely applied to various plasma waves to better identify naturally occurring waves during periods of instrument interference. The occurrence rate of ECH waves in higher harmonic bands is comparable to that in the first harmonic band, except in the noon-to-dusk sector. As the level of geomagnetic activity increases, ECH waves in all bands can be observed at lower L-shells. The occurrence rates of weak (moderate, strong) waves in all four bands increase 3-4 (4-6, 5-10) times during disturbed periods compared to those during quiet periods. The current results may provide better understanding of ECH-driven magnetosphere-ionosphere coupling.
通讯机构：
[Rui Xiong] K;[Zhihong Lu] T;The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China<&wdkj&>School of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China<&wdkj&>Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072, China
摘要：
Half-metallic chromium dioxide (CrO(2)) is an ideal spintronic material due to its near-full spin polarization and ultralow Gilbert damping at room temperature. Based on theoretical calculations, we found that the tunneling magnetoresistance (TMR) ratios of the CrO(2)/XO(2)/CrO(2) (X= Ti and Sn) magnetic tunnel junctions (MTJs) can reach up to the order of magnitude of 10(5)%, and the magnetoresistance (MR) ratio of CrO(2)/RuO(2)/CrO(2) magnetic junctions (MJs) can reach the order of magnitude of 10(4)%. In addition, we succeeded in fabricating epitaxial CrO(2)-based MTJs (CrO(2)/TiO(2)/CrO(2) and CrO(2)/TiO(2)/Co(2)FeAl) with TiO(2) tunnel barriers of varying thickness. Evident TMR effects were observed for all CrO(2)-based MTJs with the highest MR ratio of 8.55% for the CrO(2)/TiO(2)/Co(2)FeAl MTJ at 10 K. The MR ratios of CrO(2)-based MTJs in our studies were lower than theoretical expectations, which could be due to the possible mixture of interface atoms and Cr magnetization reversal. Moreover, the existence of oxygen vacancies in the TiO(2) tunnel barrier also weakened the TMR effect significantly due to increased spin scattering, and the annealing treatment in an oxygen atmosphere led to an increase in the MR ratio of the CrO(2)/TiO(2)/Co(2)FeAl MTJ by about 33% in comparison with the unannealed MTJ, which is consistent with theoretical calculations.
