Large-Quantity Synthesis of Single-Crystalline Metal Indium Nano/Sub-Micron Wires

Large quantities of metal indium single-crystalline wires with diameters ranging from tens of nanometres to a few micrometres were synthesized on Si substrates. Unlike traditional methods for the fabrication of nanowires or nanorods, liquid indium was squeezed out of the pores and cracks from porous an InAlN layer to form the wires. Continuous pushing out of liquid metal indium under strength, lowering of liquid-solid interfaces and the confinement of the cracks all contribute to the growth of indium wires. Our experiments have shed some light on the possibility of synthesizing large quantities quasi-1D nano/sub-micron structures with specified cross-sectional geometry using the similar method.     

Topological transport in Dirac electronic systems:A concise review

Various novel physical properties have emerged in Dirac electronic systems, especially the topological characters protected by symmetry. Current studies on these systems have been greatly promoted by the intuitive concepts of Berry phase and Berry curvature, which provide precise definitions of the topological phases. In this topical review, transport properties of topological insulator(Bi2Se3), topological Dirac semimetal(Cd3As2), and topological insulator-graphene heterojunction are presented and discussed. Perspectives about transport properties of two-dimensional topological nontrivial systems,including topological edge transport, topological valley transport, and topological Weyl semimetals, are provided.     

Tapered dielectric structure in metal as a wavelength-selective surface plasmon polariton focuser

Symmetric tapered dielectric structures in metal have demonstrated applications such as the nanofocusing of surface plasmon polaritons, as well as the waveguiding of V-channel polaritons. Yet the fabrication of smooth-surfaced tapered structure remains an obstacle to most researchers. We have successfully developed a handy method to fabricate metal-sandwiched tapered nanostructures simply with electron beam lithography. Though these structures are slightly different from conventional symmetric V-shaped structures, systematic simulations show that similar functionality of surface plasmon polariton nanofocusing can still be achieved. When parameters are properly selected, wavelength-selective nanofocusing of surface plasmon polaritons can be obtained.     

拓扑半金属-超导体异质结的约瑟夫森效应

拓扑半金属是一类受对称性保护的无能隙量子材料.因其相对论性能带色散关系,拓扑半金属中涌现出丰富的量子态和量子效应,例如费米弧表面态和手征反常.近年来,因在拓扑量子计算的潜在应用,拓扑与超导的耦合体系受到广泛关注.本文从两方面回顾拓扑半金属-超导体异质结体系近年来的实验进展:1)超导电流对拓扑量子态的模式过滤; 2)拓扑超导和Majorana零能模的探测与调控.对于前者,利用约瑟夫森电流对电磁场的响应,拓扑半金属中费米弧表面态的弹道输运被揭示,高阶拓扑半金属相被证实,有限动量配对及超导二极管效应被实现.对于后者,通过交流约瑟夫森效应,狄拉克半金属中4π周期的拓扑超导态被发现,纯电学栅压调控的拓扑相变被实现.本文最后展望了拓扑半金属-超导体异质结体系的发展前景和在Majorana零能模编织和拓扑量子计算上的潜在应用.     

Orbit-Transfer Torque Driven Field-Free Switching of Perpendicular Magnetization

he reversal of perpendicular magnetization （PM） by electric control is crucial for high-density integration of low-power magnetic random-access memory.Although the spin-transfer torque and spin-orbit torque technologies have been used to switch the magnetization of a free layer with perpendicular magnetic anisotropy,the former has limited endurance because of the high current density directly through the junction,while the latter requires an external magnetic field or unconventional configuratio...     

Strain Tunable Berry Curvature Dipole,Orbital Magnetization and Nonlinear Hall Effect in WSe_2 Monolayer

The electronic topology is generally related to the Berry curvature,which can induce the anomalous Hall effect in time-reversal symmetry breaking systems.Intrinsic monolayer transition metal dichalcogenides possesses two nonequivalent K and K’ valleys,having Berry curvatures with opposite signs,and thus vanishing anomalous Hall effect in this system.Here we report the experimental realization of asymmetrical distribution of Berry curvature in a single valley in monolayer WSe₂ via applying uniaxial strain to break C_3v symmetry.As a result,although the Berry curvature itself is still opposite in K and K’ valleys,the two valleys would contribute equally to nonzero Berry curvature dipole.Upon applying electric field E,the emergent Berry curvature dipole D would lead to an out-of-plane orbital magnetization M ∝ D·E,which further induces an anomalous Hall effect with a linear response to E²,known as nonlinear Hall effect.We show the strain modulated transport properties of nonlinear Hall effect in monolayer WSe₂ with moderate hole-doping by gating.The second-harmonic Hall signals show quadratic dependence on electric field,and the corresponding orbital magnetization per current density M/J can reach as large as 60.In contrast to the conventional Rashba-Edelstein effect with in-plane spin polarization,such current-induced orbital magnetization is along the out-of-plane direction,thus promising for high-efficient electrical switching of perpendicular magnetization.     

Bulk-Quantity Synthesis and Conductive Properties of Comb-Like Dendritic ZnO Nanostructures

Adopting a simple low-temperature (-500℃) vapour process, we have synthesized bulk quantity comb-like dendritic ZnO nanostructures in large area. An atomic force microscope equipped with Au-coated probes was employed to elucidate the current-voltage characteristic of the individual ZnO nanocomb. The connection electrodes were defined by depositing Pt wires using focused ion beam (FIB). A rectification effect was observed,while it was slightly suppressed compared with that of the previous reports. The good conductive properties of the sample can be attributed to the Ga ions implantation through the FIB process of electrode definition. We suggest that the material and the FIB method can be developed to fabricate novel nanosized devices.     

Defect-Related Photoresponse and Polarization-Sensitive Photodetection of Single ZnO Nanowires

Defect-related photoconductivity of single ZnO nanowires is investigated. The photoconductivity shows powerlaw dependence with incident green laser intensity due to the defect mechanisms including both recombination centres and traps. The device based on single ZnO nanowire shows a sensitive photoresponse to green light with significant on/off ratios. In addition, the photocurrent ＆ highly sensitive to the polarization of the incident illumination. Therefore, the nanowire may act as a polarized photodetector.