Spin-current diode with a ferromagnetic semiconductor

Diode is a key device in electronics: the charge current can flow through the device under a forward bias, while almost no current flows under a reverse bias. Here we propose a corresponding device in spintronics: the spin-current diode, in which the forward spin current is large but the reversed one is negligible. We show that the lead/ferromagnetic quantum dot/lead system and the lead/ferromagnetic semiconductor/lead junction can work as spin-current diodes. The spin-current diode, a low dissipation device, may have important applications in spintronics, as the conventional charge-current diode does in electronics.Comment: 5 pages, 3 figure

The spin-polarized ν=0\nu=0 state of graphene: a spin superconductor

We study the spin-polarized $\nu=0$ Landau-level state of graphene. Due to the electron-hole attractive interaction, electrons and holes can bound into pairs. These pairs can then condense into a spin-triplet superfluid ground state: a spin superconductor state. In this state, a gap opens up in the edge bands as well as in the bulk bands, thus it is a charge insulator, but it can carry the spin current without dissipation. These results can well explain the insulating behavior of the spin-polarized $\nu=0$ state in the recent experiments.Comment: 6 pages, 4 figure

Theory for electric dipole superconductivity with an application for bilayer excitons

Exciton superfluid is a macroscopic quantum phenomenon in which large quantities of excitons undergo the Bose-Einstein condensation. Recently, exciton superfluid has been widely studied in various bilayer systems. However, experimental measurements only provide indirect evidence for the existence of exciton superfluid. In this article, by viewing the exciton in a bilayer system as an electric dipole, we provide a general theory for the electric dipole superconductivity, and derive the London-type and Ginzburg-Landau-type equations for the electric dipole superconductors. By using these equations, we discover the Meissner-type effect and the electric dipole current Josephson effect. These effects can provide direct evidence for the formation of the exciton superfluid state in bilayer systems and pave new ways to drive an electric dipole current.Comment: 10 pages, 5 figures, 1 Supplementary Informatio

Topological Imbert-Fedorov shift in Weyl semimetals

The Goos-H\"anchen (GH) shift and the Imbert-Fedorov (IF) shift are optical phenomena which describe the longitudinal and transverse lateral shifts at the reflection interface, respectively. Here, we report the GH and IF shifts in Weyl semimetals (WSMs) - a promising material harboring low energy Weyl fermions, a massless fermionic cousin of photons. Our results show that GH shift in WSMs is valley-independent which is analogous to that discovered in a 2D relativistic material - graphene. However, the IF shift has never been explored in non-optical systems, and here we show that it is valley-dependent. Furthermore, we find that the IF shift actually originates from the topological effect of the system. Experimentally, the topological IF shift can be utilized to characterize the Weyl semimetals, design valleytronic devices of high efficiency, and measure the Berry curvature

Adaptive noise cancellation using multichannel lattice structure.

This thesis presents a multichannel adaptive noise cancellation technique (MCLS) for cancelling the noise over nonlinear transmission channel. The technique applies to the situation in which the reference signal and noisy primary signal are collected simultaneously. The coefficients of the multichannel multiple regression transversal filter are modified adaptively according to the backward prediction error vector generated from the multichannel adaptive lattice predictor. This multichannel adaptive noise cancellation procedure involves the NLMS adaptive algorithm. The performance of the new technique using different types of transmission channels, different types of reference inputs and different types of noise-free primary inputs are examined analytically. The new approach is experimentally shown to have better noise cancellation performance than the existing single-channel adaptive lattice noise cancellation algorithm (SCLS) over nonlinear transmission channel case, especially in low input SNR situation.Dept. of Electrical and Computer Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2004 .X54. Source: Masters Abstracts International, Volume: 43-01, page: 0288. Adviser: H. K. Kwan. Thesis (M.A.Sc.)--University of Windsor (Canada), 2004

English Major Undergraduates’ Needs and Perceptions of Business English Activities and Resources in a Chinese University

This article explores English major undergraduates’ views on business English skills and topics, and investigates their perceptions of the meaningful activities and resources in one Chinese university context. The main research instruments are questionnaires containing rating and open-ended questions, and researcher’s participant observation with 149 English major undergraduates enrolling in Business English courses in 2016. The results show that participants most often require improvement in note-taking skills, public speaking and need to learn business communication topics. Participants value communicative teaching methodologies, including role plays, oral presentation, theme-based discussion, games and group work. Participants more often rely on electronic media resources, such as videos, internet and mobile applications than the print media resources such as library, books and dictionaries. This study serves as basis for further business English curriculum development and resources provision in the higher education setting. The study also indicates the potential for business English resources development and exploitation in China within the international education environment