物理学研究生专业英语的课程教学模式改革与探索

物理学专业英语是物理学研究生教育中的基础课程,被设置为研究生课程的必修课。本文针对非英语专业的研究生英语课程教学的现状及存在的问题,如教学内容陈旧、教学形式单一、教学成效不佳等,结合物理学专业的特点,对研究生专业英语的教学内容设置与教学实践方式等方面进行教学改革与创新,并对改革效果进行总结与反思。

Electronic property and topological phase transition in a graphene/CoBr_(2) heterostructure

Recently,significant experimental advancements in achieving topological phases have been reported in van der Waals(vdW)heterostructures involving graphene.Here,using first-principles calculations,we investigate graphene/CoBr_(2)(Gr/CoBr_(2))heterostructures and find that an enhancement of in-plane magnetic anisotropy(IMA)energy in monolayer CoBr_(2) can be accomplished by reducing the interlayer distance of the vdW heterostructures.In addition,we clarify that the enhancement of IMA energy primarily results from two factors:one is the weakness of the Co-d_(xy) and Co-d_(x^(2)-y^(2)) orbital hybridization and the other is the augmentation of the Co-d_(yz) and Co-d_(z)2 orbital hybridization.Meanwhile,calculation results suggest that the Kosterlitz–Thouless phase transition temperature(TKT)of a 2D XY magnet Gr/CoBr_(2)(23.8 K)is higher than that of a 2D XY monolayer CoBr_(2)(1.35 K).By decreasing the interlayer distances,the proximity effect is more pronounced and band splitting appears.Moreover,by taking into account spin–orbit coupling,a band gap of approximately 14.3 meV and the quantum anomalous Hall effect(QAHE)are attained by decreasing the interlayer distance by 1.0 A.Inspired by the above conclusions,we design a topological field transistor device model.Our results support that the vdW interlayer distance can be used to modulate the IMA energy and QAHE of materials,providing a pathway for the development of new low-power spintronic devices.

本科生学业导师制对促进学风建设的探究

学业导师制作为一种新型的人才培养制度,有助于学生综合素质的提升,同时也有助于建立新型的师生关系,这为解决学风建设中的问题提供一种新途径。文章以建设良好的学风为目的,在明确学业导师的职责及学风中存在的主要问题的基础之上,首先探索了学业导师制相关的制度建设,然后提出了建立良好师生关系的方法,在此基础之上,提出了几条措施来促进学风建设,最后尝试将这些研究成果进行实施推广。

Two-dimensional transition metal halide PdX_(2)(X=F,Cl,Br,I):A promising candidate of bipolar magnetic semiconductors

Two-dimensional(2D)nanomaterials with bipolar magnetism show great promise in spintronic applications.Manipulating carriers'spin-polarized orientation in bipolar magnetic semiconductor(BMS)requires a gate voltage,but that is volatile.Recently,a new method has been proposed to solve the problem of volatility by introducing a ferroelectric gate with proper band alignment.In this paper,we predict that the PdX_(2)(X=F,Cl,Br,I)monolayers are 2D ferromagnetic BMS with dynamic stability,thermal stability,and mechanical stability by first-principles calculations.The critical temperatures are higher than the boiling point of liquid nitrogen and the BMS characteristics are robust against external strains and electric fields for PdCl_(2) and PdBr_(2).Then,we manipulate the spin-polarization of PdCl_(2) and PdBr_(2) by introducing a ferroelectric gate to enable magnetic half-metal/semiconductor switching and spin-up/down polarization switching control.Two kinds of spin devices(multiferroic memory and spin filter)have been proposed to realize the spin-polarized directions of electrons.These results demonstrate that PdCl_(2) and PdBr_(2) with BMS characters can be widely used as a general material structure for spintronic devices.

Prediction of one-dimensional CrN nanostructure as a promising ferromagnetic half-metal

Searching for one-dimensional(1D)nanostructure with ferromagnetic(FM)half-metallicity is of significance for the development of miniature spintronic devices.Here,based on the first-principles calculations,we propose that the 1D CrN nanostructure is a FM half-metal,which can generate the fully spin-polarized current.The ab initio molecular dynamic simulation and the phonon spectrum calculation demonstrate that the 1D CrN nanostructure is thermodynamically stable.The partially occupied Cr-d orbitals endow the nanostructure with FM half-metallicity,in which the half-metallic gap(?s)reaches up to 1.58 eV.The ferromagnetism in the nanostructure is attributed to the superexchange interaction between the magnetic Cr atoms,and a sizable magnetocrystalline anisotropy energy(MAE)is obtained.Moreover,the transverse stretching of nanostructure can effectively modulate?s and MAE,accompanied by the preservation of half-metallicity.A nanocable is designed by encapsulating the CrN nanostructure with a BN nanotube,and the intriguing magnetic and electronic properties of the nanostructure are retained.These novel characteristics render the 1D CrN nanostructure as a compelling candidate for exploiting high-performance spintronic devices.

Spin–orbit stable dirac nodal line in monolayer B_(6)O

The two-dimensional(2D) materials with nodal line band crossing have been attracting great research interest. However, it remains a challenge to find high-stable nodal line structure in 2D systems. Herein, based on the first-principles calculations and theoretical analysis, we propose that monolayer B_(6)O possesses symmetry protected Dirac nodal line(DNL)state, with its Fermi velocity of 10^(6)m/s in the same order of magnitude as that of graphene. The origin of DNL fermions is induced by coexistence of time-reversal symmetry and inversion symmetry. A two-band tight-binding model is further given to understand the mechanism of DNL. Considering its robustness against spin–orbit coupling(SOC) and high structural stability, these results suggest monolayer B_(6)O as a new platform for realizing future high-speed low-dissipation devices.

Discovery of Two-Dimensional Quantum Spin Hall Effect in Triangular Transition-Metal Carbides

Though the quantum spin Hall effect（QSHE） in two-dimensional（2 D） crystals has been widely explored, the experimental realization of quantum transport properties is only limited to HgTe/CdTe or InAs/GaSb quantum wells. Here we employ a tight-binding model on the basis of d（z^2）, d（xy）, and d（x^2-y^2） orbitals to propose QSHE in the triangular lattice, which are driven by a crossing of electronic bands at the Γ point. Remarkably, 2 D oxidized Mxenes W2 M2 C3 are ideal materials with nontrivial gap of 0.12 eV, facilitating room-temperature observations in experiments. We also find that the nontrivially topological properties of these materials are sensitive to the cooperative effect of the electron correlation and spin-orbit coupling. Due to the feasible exfoliation from its 3 D MAX phase, our work paves a new direction towards realizing QSHE with low dissipation.