Pseudospin-filter tunneling of massless Dirac fermions

The tunneling of the massless Dirac fermions through a vector potential barrier are theoretically investigated, wherethe vector potential can be introduced by very high and very thin (d-function) magnetic potential barriers. We showthat, distinct from the previously studied electric barrier tunneling, the vector potential barriers are more transparent forpseudospin-1/2 Dirac fermions but more obstructive for pseudospin-1 Dirac fermions. By tuning the height of the vectorpotential barrier, the pseudospin-1/2 Dirac fermions remain transmitted, whereas the transmission of the pseudospin-1Dirac fermions is forbidden, leading to a pseudospin filtering effect for massless Dirac fermions.

Unsuitable use of spin and pseudospin symmetries with a pseudoscalar Cornell potential

The concepts of spin and pseudospin symmetries has been used as mere rhetorics to decorate the pseudoscalar potential [Chin. Phys. B 22 090301 （2013）]. It is also pointed out that a more complete analysis of the bound states of fermions in a pseudoscalar Cornell potential has already been published elsewhere.

Exact solution of Dirac equation for Scarf potential with new tensor coupling potential for spin and pseudospin symmetries using Romanovski polynomials

The bound state solutions of Dirac equations for a trigonometric Scarf potential with a new tensor potential under spin and pseudospin symmetry limits are investigated using Romanovski polynomials. The proposed new tensor potential is inspired by superpotential form in supersymmetric （SUSY） quantum mechanics. The Dirac equations with trigonometric Scarf potential coupled by a new tensor potential for the pseudospin and spin symmetries reduce to Schrtdinger-type equations with a shape invariant potential since the proposed new tensor potential is similar to the superpotential of trigonometric Scarf potential. The relativistic wave functions are exactly obtained in terms of Romanovski polynomials and the relativistic energy equations are also exactly obtained in the approximation scheme of centrifugal term. The new tensor potential removes the degeneracies both for pseudospin and spin symmetries.

Properties of pseudospin polarization on a graphene-based spin singlet superconducting junction

We investigate theoretically transport characteristics in a graphene-based pseudospinmagnet/superconductor junction, including the s-wave and the d-wave pairing symmetry potential in the superconducting region. It is found that the pseudospin polarization, in sharp contrast to spin polarization in the graphene-based ferromagnet/superconductor junction, holds no influence on the specular Andreev reflection for a negligible Fermi energy. Furthermore, the Fano factor is cru-ially affected by the zero bias state. Therefore, we suggest here that the findings could shed light on the realization of graphene-based pseudospintronics devices and provide a new way to detect the specular Andreev reflection and the zero bias state in the actual experiments.

Current-induced pseudospin polarization in silicene

The pseudospin polarization induced by an external electric field in silicene in the presence of weakly spin- independent impurities is considered theoretically in the linear response regime based on Green＇s function method. We study the effects of the interplay between the sublattice potential and the intrinsic spin orbit coupling on the pseudospin polarization. We show that the pseudospin polarization perpendicular to the electric field is independent of the impurity parameter, while the pseudospin polarization in the direction of the electric field is sensitive to the impurity parameter. The dependences of the pseudospin polarizations on the chemical potential are studied.

Pseudoscalar Cornell potential for a spin-1/2 particle under spin and pseudospin symmetries in 1+1 dimension

The Cornell potential that consists of Coulomb and linear potentials has received a great deal of attention in particle physics. In this paper, we present the exact solutions of the Dirac equation with the pseudoscalar Cornell potential under spin and pseudospin symmetry limits. The energy eigenvalues and corresponding eigenfunctions are given in closed form.

Acoustic topological phase transition induced by band inversion of high-order compound modes and robust pseudospin-dependent transport

A simple two-dimensional phononic crystal hosting topologically protected edge states is proposed to emulate the quantum spin Hall effect in electronic systems, whose phononic topological phase can be reconfigured through the rotation of scatters. In particular, the band inversion occurs between two pairs of high-order compound states, resulting in topological phase transition from trivial to nontrivial over a relatively broad high-frequency range. This is further evidenced by an effective Hamiltonian derived by the k·p perturbation theory. The phononic topology is related to a pseudo-timereversal symmetry constructed by the point group symmetry of two doubly degenerate eigenstates. Numerical simulations unambiguously demonstrate robust helical edge states whose pseudospin indices are locked to the propagation direction along the interface between topologically trivial and nontrivial phononic crystals. Our designed phononic systems provide potential applications in robust acoustic signal transport along any desired path over a high-frequency range.

The ground states and pseudospin textures of rotating two-component Bose–Einstein condensates trapped in harmonic plus quartic potential

The ground states of two-component miscible Bose–Einstein condensates（BECs） confined in a rotating annular trap are obtained by using the Thomas–Fermi（TF） approximation method.The ground state density distribution of the condensates experiences a transition from a disc shape to an annulus shape either when the angular frequency increases and the width and the center height of the trap are fixed,or when the width and the center height of the trap increase and the angular frequency is fixed.Meantime the numerical solutions of the ground states of the trapped two-component miscible BECs with the same condition are obtained by using imaginary-time propagation method.They are in good agreement with the solutions obtained by the TF approximation method.The ground states of the trapped two-component immiscible BECs are also given by using the imaginary-time propagation method.Furthermore,by introducing a normalized complex-valued spinor,three kinds of pseudospin textures of the BECs,i.e.,giant skyrmion,coaxial double-annulus skyrmion,and coaxial three-annulus skyrmion,are found.

Spin and pseudospin symmetries of the Dirac equation with shifted Hulthe′n potential using supersymmetric quantum mechanics

In this paper, we obtain approximate analytical solutions of the Dirac equation for the shifted Hulthén potential within the framework of spin and pseudospin symmetry limits for arbitrary spin–orbit quantum number κ using the supersymmetry quantum mechanics. The energy eigenvalues and the corresponding Dirac wave functions are obtained in closed forms.

Pseudospin-induced chirality with staggered optical graphene

Pseudospin has an important role in understanding many interesting physical phenomena that are associated with twodimensional materials such as graphene.Pseudospin has been proposed to be directly related to angular momentum,and orbital angular momentum was recently experimentally demonstrated to be an intrinsic property of pseudospin in a photonic honeycomb lattice.However,in photonics,the interaction between spin and pseudospin for light has not been investigated.In this letter,we propose that in an optical analog of staggered graphene(that is,a photonic honeycomb lattice waveguide with in-plane inversion symmetry breaking),the pseudospin mode can strongly couple to the spin of an optical beam that is incident in certain directions.The spin-pseudospin coupling that is caused by the spin-orbit conversion in the scattering process induces a strong optical chiral effect for the transmitted optical beam.Spin-pseudospin coupling of light opens the door to the design of pseudospin-mediated spin or valley-selective photonic devices.

Perturbative pseudospin symmetry limit with linear spin-orbit potential

The pseudospin symmetry （PSS） limits which conserve substantial spin-orbit splitting are investigated. It is found that while the strength of the spin-orbit potential as well as the spin-orbit splitting increase, the pseudospin doublets, e.g., 2p3/2 and lf5/2 states, are always degenerate. Furthermore, by examining the perturbation corrections to the single-particle energies, the perturbative nature of the proposed PSS limits is also discussed.

Spin and Pseudospin Symmetries of Dirac Equation and the Yukawa Potential as the Tensor Interaction

Considering of a tensor interaction in Dirac equation removes the degeneracy in spin and pseudospin doublets and consequently leads to results consistent with the experimental data. Here, instead of the commonly used Coulomb or linear terms, we investigate a tensor interaction of Yukawa form. We obtain arbitrary state solutions of Dirac equation under vector, scalar and tensor Yukawa potentials via a physical approximation and the Nikiforov-Uvarov methodology. The solutions are discussed in detail.

Influence of different fields of mesons on the pseudospin symmetry in single-neutron resonant states

In the framework of the relativistic mean field theory combined with the complex momentum representation method,we elucidate the pseudospin symmetry in the single-neutron resonant states and its dependence on the σ,ω,and ρ meson fields.Compared with the effect of theρfield,the τandωfields provide the main contributions to the pseudospin energy and width splitting of the resonant pseudospin doublets.Especially,we compare quantitatively the pseudospin wave functions's plittings in resonant doublets,and investigate their dependencies on different fields of mesons,which is consistent with that of energy and width splittings.Current research is helpful to understand the mechanism and properties of pseudospin symmetry for resonant states.

Massive Dirac particles based on gapped graphene with Rosen-Morse potential in a uniform magnetic field

We explore the gapped graphene structure in the two-dimensional plane in the presence of the Rosen-Morse potential and an external uniform magnetic field.In order to describe the corresponding structure,we consider the propagation of electrons in graphene as relativistic fermion quasi-particles,and analyze it by the wave functions of two-component spinors with pseudo-spin symmetry using the Dirac equation.Next,to solve and analyze the Dirac equation,we obtain the eigenvalues and eigenvectors using the Legendre differential equation.After that,we obtain the bounded states of energy depending on the coefficients of Rosen-Morse and magnetic potentials in terms of quantum numbers of principal n and spin-orbit k.Then,the values of the energy spectrum for the ground state and the first excited state are calculated,and the wave functions and the corresponding probabilities are plotted in terms of coordinates r.In what follows,we explore the band structure of gapped graphene by the modified dispersion relation and write it in terms of the two-dimensional wave vectors K_(x) and K_(y).Finally,the energy bands are plotted in terms of the wave vectors K_(x) and K_(y) with and without the magnetic term.

三轴形变核^(131)Ba中的奇异集体激发模式

利用意大利Legnaro实验室串列静电加速器提供的65 MeV^(13)C束流与122Sn靶的熔合蒸发反应布居了^(131)Ba的高自旋态,并搭建了新的能级纲图.新的能级纲图由15条转动带组成,包括三对手征双重带,其中两对正宇称手征带为赝自旋-手征四重带.正负宇称手征带通过一系列增强的E1跃迁连接,表明它们之间存在八极关联.在低自旋区域搭建了一条新的转动带,通过一系列γ跃迁向νh1_(1/2)晕带退激.这种能级结构与摇摆带相似,但基于现有的实验证据还难以将它确认为摇摆带,不能排除其他集体激发机制,如γ振动的影响.

基于结构反转二维光子晶体的拓扑相变及拓扑边界态的构建

构建了二维六角蜂窝晶格的两种结构,让散射体和基体材料反转.由于特有的点群对称,该晶格在布里渊区中心具有类比电子体系的p轨道和d轨道.在散射体和基体反转的两种结构中, p轨道和d轨道也直接实现了反转.定量分析了产生轨道反转的原因来自于低频局域共振产生空气带和介质带的反转.通过p轨道和d轨道的宇称特性,构建了类比电子体系量子自旋霍尔效应的赝自旋态.通过Γ点处有效哈密顿量的分析,揭示轨道反转导致的拓扑相变.通过结构的优化,构建了基于赝自旋的拓扑边界态.电磁波仿真模拟和能流矢量分析证明了结构具有电子体系量子自旋霍尔效应的特性,即自旋与传播方向锁定和拓扑保护.结果也证明经典波量子自旋霍尔效应的实现可以不经历带隙关闭的过程.与同类型的研究相比较,本文的结构不需要晶格的缩放,具有设计简单、带隙宽和边界态局域性较强的特点.

Approximate any 1-state solutions of the Dirac equation for modified deformed Hylleraas potential by using the Nikiforov—Uvarov method

We investigate the spin and pseudospin symmetries of the Dirac equation under modified deformed Hylleraas potential via a Pekeris approximation and the Nikiforov-Uvarov technique. A tensor interaction of Coulomb form is considered and its degeneracy-removing role is discussed in detail. The solutions are reported for an arbitrary quantum number in a compact form and useful numerical data are included.

SP(6)模型在复合粒子表象理论中的近似表示

运用复合粒子表象理论给出了费米子动力学对称SP(6)模型在s.d玻色子空间中的近似表示,并与精确的Dyson玻色子映像结果作一比较。

相对论平均场理论关于赝自旋对称性的研究(英文)

相对论平均场理论被应用于检查208Pb的赝自旋对称性.通过相对论平均场计算提取的赝自旋伙伴态的波函数劈裂,研究不同介子场和光子场对赝自旋对称性的影响.结果表明:赝自旋波函数劈裂随着σ介子场强度的增加而增大,随着ω介子场强度的增加而减小.相比于σ和ω介子场,ρ介子场和光子场仅对赝自旋劈裂起着微弱的影响,σ和ω介子场对赝自旋对称性起主导作用,赝自旋劈裂主要来源于σ和ω介子场的竞争.

含改进Tietz-Hua势Dirac方程的赝自旋对称解析解

基于施图姆-刘维尔理论和形状不变性原理,采用Pekeris类型的近似方法,唯象地研究了具有改进Tietz-Hua势场标量和矢量核子势的原子核中单核子的赝自旋对称.解析求解了系统的能量方程和旋量波函数,并通过数值求解能量方程,验证了单核子谱的赝自旋对称性.