Spin-Orbit Splitting in Semiconductor Quantum Dots with a Two-Dimensional Ring Model

We present a theoretical study of the energy levels with two-dimensional ring confining potential in the presence of the Rashba spin-orbit interaction. The features of some low-lying states in various strengths of the Rashba spin-orbit interaction are investigated. The Rashba spin-orbit splitting can a/so be influenced by the width of the potential barrier. The computed results show that the spin-polarized electronic states can be more easily achieved in a weakly confined dot when the confinement strength for the Rashba spin-orbit interaction is larger than a critical value.     

Back-to-back emission of the electrons in double photoionization of helium

We calculate the double differential distributions and distributions in recoil momenta for the high energy non-relativistic double photoionization of helium atom. We show that the results of recent experiments provide the pioneering experimental manifestation of the quasifree mechanism for the double photoionization which was predicted long ago in our papers. This mechanism provides a surplus in distribution over the recoil momenta at small values of the latter, corresponding to nearly ??back-to-back?? emission of the photoelectrons. Also, in agreement with previous analysis we demonstrate that this surplus is due to the quadrupole terms of the photon-electron interaction. We present the characteristic angular distribution for the back-to-back electron emission. The confirmation of the quasifree mechanism existence opens a new area for exciting experiments, which are expected to increase our understanding of the electron dynamics and of the bound states structure.     

Rashba spin-orbit interaction and shot noise for spin-polarized and entangled electrons

We study shot noise for spin-polarized currents and entangled electron pairs in a four-probe (beam-splitter) geometry with a local Rashba spin-orbit (s-o) interaction in the incoming leads. Within the scattering formalism we find that shot noise exhibits Rashba-induced oscillations with continuous bunching and antibunching. We show that entangled states and triplet states can be identified via their Rashba phase in noise measurements. For two-channel leads, we find an additional spin rotation due to s-o induced interband coupling which enhances spin control. We show that the s-o interaction deter-mines the Fano factor, which provides a direct way to measure the Rashba coupling constant via noise.     

Quantum dot with spin-orbit interaction in noncommutative phase space and analog Landau levels

We have studied a quantum dot with Rashba spin-orbit interaction in noncommutative phase space. The energy eigenvalues are analogous to Landau energy levels. It is shown that this system is related with a physically realizable model of a quantum dot with Rashba spin-orbit interaction in a magnetic field whereby a relation is derived among the noncommutative parameters, spin-orbit coupling strength and magnetic field.     

金属表面Rashba自旋轨道耦合作用研究进展

自旋轨道耦合是电子自旋与轨道相互作用的桥梁, 它提供了利用外电场来调控电子的轨道运动、进而调控电子自旋状态的可能. 固体材料中有很多有趣的物理现象, 例如磁晶各向异性、自旋霍尔效应、拓扑绝缘体等, 都与自旋轨道耦合密切相关. 在表面/界面体系中, 由于结构反演不对称导致的自旋轨道耦合称为Rashba自旋轨道耦合, 它最早在半导体材料中获得研究, 并因其强度可由栅电压灵活调控而备受关注, 成为电控磁性的重要物理基础之一. 继半导体材料后, 金属表面成为具有Rashba自旋轨道耦合作用的又一主流体系. 本文以Au(111), Bi(111), Gd(0001)等为例综述了磁性与非磁性金属表面Rashba自旋轨道耦合的研究进展, 讨论了表面电势梯度、原子序数、表面态波函数的对称性, 以及表面态中轨道杂化等因素对金属表面Rashba自旋轨道耦合强度的影响. 在磁性金属表面, 同时存在Rashba自旋轨道耦合作用与磁交换作用, 通过Rashba自旋轨道耦合可能实现电场对磁性的调控. 最后, 阐述了外加电场和表面吸附等方法对金属表面Rashba自旋轨道耦合的调控. 基于密度泛函理论的第一性原理计算和角分辨光电子能谱测量是金属表面Rashba自旋轨道耦合的两大主要研究方法, 本文综述了这两方面的研究结果, 对金属表面Rashba自旋轨道耦合进行了深入全面的总结和分析.     

Third harmonic generation in quantum dot with Rashba spin orbit interaction

Here we have investigated the influence of magnetic field and confinement potential on nonlinear optical property, third harmonic generation (THG) of a parabolically confinement quantum dot in the presence of Rashba spin orbit interaction. We have used density matrix formulation for obtaining optical properties within the effective mass approximation. The results are presented as a function of confining potential, magnetic field, Rashba spin orbit interaction strength and photon energy. Our results indicate that an increase of Rashba spin orbit interaction coefficient produces strong effect on the peak positions of THG. The role of confinement strength and spin orbit interaction strength as control parameters on THG have been demonstrated.     

Microscopic description of collective motion in pf shell nuclei

Rotational and vibrational excitations in pf shell nuclei are studied by means of the generator coordinate method. The generator coordinates are the pairing energies and the quadrupole moments of constrained Hartree-Bogoliubov states, projected onto good angular momenta and particle numbers. The Kuo interaction and the one modified by McGrory are used. The vibrational character of the yrast energies appears to be produced by mixing prolate and oblate wave functions. Pairing correlations are essential for this mixing. In contrast to the yrast states the excitation energies of the higher states depend strongly on the interaction used. They show good agreement with experiment, particularly in the case of ⁴⁸Ti with the Kuo force. The calculated B(E2) values exhibit a rotational band structure in general, even if the energies look more vibrational. The force dependence of the excitation energies can qualitatively be understood by inspection of the intrinsic energy surface.     

Polaron and molecular states of a spin–orbit coupled impurity in a spinless Fermi sea

We investigate the polaron and molecular states of a fermionic atom with one-dimensional spin–orbit coupling(SOC)coupled to a three-dimensional spinless Fermi sea. Because of the interplay among the SOC, Raman coupling and spinselected interatomic interactions, the polaron state induced by the spin–orbit coupled impurity exhibits quite unique features. We find that the energy dispersion of the polaron generally has a double-minimum structure, which results in a finite center-of-mass(c.m.) momentum in the ground state, different from the zero-momentum polarons where SOC are introduced into the majority atoms. By further tuning the parameters such as the atomic interaction strength, a discontinuous transition between the polarons with different c.m. momenta may occur, signaled by the singular behavior of the quasiparticle residue and effective mass of the polaron. Meanwhile, the molecular state as well as the polaron-to-molecule transition is also strongly affected by the Raman coupling and the effective Zeeman field, which are introduced by the lasers generating SOC on the impurity atom. We also discuss the effects of a more general spin-dependent interaction and mass ratio. These results would be beneficial for the study of impurity physics brought by SOC.     

单轴应变对H在α-Fe中占位及扩散的影响

采用基于密度泛函理论的第一性原理方法,研究了H在不同单轴应变下α-Fe中的间隙占位,计算了H原子的溶解能、态密度、电荷差分密度和电荷布居.结果表明:不同单轴拉压应变作用下,H原子优先占据四面体间隙(Ts)位,且随着压应变减小、拉应变增加,H原子越易溶于α-Fe.压应变使得Ts位的H获得更多的电子,而拉应变减少了这种电荷转移.应用LST/QST过渡态搜索计算垂直应变方向的扩散.八面体间隙位是邻近Ts位H的扩散过渡态.扩散激活能与应变呈线性关系,且随着压应变的增加,扩散激活能降低,扩散更容易.     

Change in the frequency and intensity of the spectral lines of a hydrogen-like atom in the field of a point charge

The changes in the wave functions and the energies of a hydrogen-like atom in the static field of a structureless charged particle are calculated in the asymptotic approximation. The corrections to the energy of states, as well as to the dipole matrix elements of radiative transitions caused by the interaction of the atom with the point charge at long range are calculated using the perturbation theory and the Sturm series for a reduced Coulomb Green’s function in parabolic coordinates. The analytical expressions are derived and tables of numerical values of the coefficients of asymptotic series that determine the corrections to the matrix elements and the intensities of transitions of the Lyman and Balmer series are presented.     

Charge and spin density response functions of the clean two-dimensional electron gas with Rashba spin-orbit coupling at finite momenta and frequencies

We analytically evaluate charge and spin density response functions of the clean two-dimensional electron gas with Rashba spin-orbit coupling at finite momenta and frequencies. On the basis of our exact expressions we discuss the accuracy of the long-wavelength and the quasiclassical approximations. We also derive the static limit of spin susceptibilities and demonstrate, in particular, how the Kohn-like anomalies in their derivatives are related to the spin-orbit modification of the Ruderman-Kittel-Kasuya-Yosida interaction. Taking into account screening and exchange effects of the Coulomb interaction, we describe the collective charge and spin density excitation modes which appear to be coupled due to nonvanishing spin-charge response function.     

Properties of a Bound Polaron under a Perpendicular Magnetic Field

We investigate the influence of a perpendicular magnetic field on a bound polaron near the interface of a polar-polar semiconductor with Rashba effect. The external magnetic field strongly changes the ground state binding energy of the polaron and the Rashba spin-orbit （SO） interaction originating from the inversion asymmetry in the heterostructure splits the ground state binding energy of the bound polaron. In this paper, we have shown how the ground state binding energy will be with the change of the external magnetic field, the location of a single impurity, the wave vector of the electron and the electron areal density, taking into account the SO coupling. Due to the presence of the phonons, whose energy gives negative contribution to the polaron＇s, the spin-splitting states of the bound polaron are more stable, and we find that in the condition of week magnetic field, the Zeeaman effect can be neglected.     

Rashba spin–orbit effect on the magnetocapacitance of a 2DEG in a diluted magnetic semiconductor

We investigate the magnetocapacitance of the two-dimensional electron gas (2DEG) embedded in diluted magnetic semiconductors in the presence of Rashba spin–orbit interaction (SOI). We present calculations on the energy spectrum and density of states and show that the tunable spin–orbit coupling and the enhanced Zeeman splitting have a strong effect on the magnetocapacitance of the structure. In the presence of Rashba SOI, a typical beating pattern with well defined node-positions in the oscillating capacitance is observed. A simple relation that predicts the positions of nodes in the beating patterns is obtained. The interplay between the total Zeeman splitting (including the s–d exchange interaction) and the Rashba SOI is discussed.     

Tunable quantum capacitance and magnetic oscillation in bilayer graphene device

We address the quantum capacitance of a bilayer graphene device in the presence of Rashba spin–orbit interaction (SOI) by applying external magnetic fields and interlayer biases. Quantum capacitance reflects the mixing of the spin-up and spin-down states of Landau levels and can be effectively modulated by the interlayer bias. The interplay between interlayer bias and Rashba SOI strongly affects magnetic oscillations. The typical beating pattern changes tuned by Rashba SOI strength, interlayer bias energy, and temperature are examined as well.     

Exchange-enhanced spin-splitting in a two-dimensional electron gas in the presence of the Rashba spin–orbit interaction

We present a theoretical study on how many-body effects can affect the spin-splitting of a two-dimensional electron gas in the presence of the Rashba spin–orbit interaction. The standard Hartree–Fock approximation and Green's function approach are employed to calculate the energy spectrum and density of states of a spin-split two-dimensional electron gas (2DEG). We find that the presence of the exchange interaction can enhance significantly the spin-splitting of a 2DEG on top of the Rashba effect. The physical reasons behind this important phenomenon are discussed.     

The role of electron correlations in the double ionization of helium by fast protons

We consider the double ionization (DI) of a helium atom by fast protons and study the role of electron correlations in this process. We develop a quantum-mechanical approach that takes into account the interaction of the emitted electrons in continuum and the dynamical charge screening of the ejected particles, which depends on their ejection kinematics. The interaction of the emitted electrons between themselves and with the core is described in the model of approximate 3C functions, while the dynamical charge screening is described by introducing effective charges of the emitted electrons and the ion core, which are determined by the particle momenta. The derived closed analytical expressions for the differential ionization cross sections have been applied to the case of a coplanar particle ejection geometry at various momenta q transferred to the atom. Analysis of our calculations has shown that the developed model describes adequately the available experimental data. Including the dynamical charge screening has a significant effect on the DI cross section and improves considerably the agreement between theory and experiment.     

Analytical Treatment of a Three-Electron-Quantum Dot Under Rashba Spin–Orbit Interaction

Bearing in mind the wide applications of quantum dots in modern technology, we theoretically investigate a three-electron-quantum dot in the presence of Rashba spin–orbit interaction by an analytical methodology. Using the Jacobi transformations as well as the hyperspherical coordinates; we separate the Hamiltonian in terms of center of mass and relative terms and thereby calculate the basic ingredients of such systems, i.e. the wavefunction and the energy spectra. We see that in some special cases, the solutions appear in the form of Bessel functions.     

Rashba spin–orbit effect on the magnetocapacitance of a 2DEG in a diluted magnetic semiconductor

We investigate the magnetocapacitance of the two-dimensional electron gas (2DEG) embedded in diluted magnetic semiconductors in the presence of Rashba spin–orbit interaction (SOI). We present calculations on the energy spectrum and density of states and show that the tunable spin–orbit coupling and the enhanced Zeeman splitting have a strong effect on the magnetocapacitance of the structure. In the presence of Rashba SOI, a typical beating pattern with well defined node-positions in the oscillating capacitance is observed. A simple relation that predicts the positions of nodes in the beating patterns is obtained. The interplay between the total Zeeman splitting (including the s–d exchange interaction) and the Rashba SOI is discussed.     

Theoretical study of the migration of the hydrogen atom adsorbed on aluminum nanowire

We study the behavior of a hydrogen atom adsorbed on aluminum nanowire based on density functional theory. In this study, we focus on the electronic structure, potential energy surface (PES), and quantum mechanical effects on hydrogen and deuterium atoms. The activation energy of the diffusion of a hydrogen atom to the axis direction is derived as 0.19 eV from PES calculations. The probability density, which is calculated by including quantum effects, is localized on an aluminum top site in both cases of hydrogen and deuterium atoms of the ground state. In addition, some excited states are distributed between aluminum atoms on the surface of the nanowire. The energy difference between the ground state and these excited states are below 0.1 eV, which is much smaller than the activation energy of PES calculations. Thus using these excited states, hydrogen and deuterium atoms may move to the axial direction easily. We also discuss the electronic structure of the nanowire surface using quantum energy density defined by one of the authors.     

Spin and Majorana polarization in topological superconducting wires

We study a one-dimensional wire with strong Rashba and Dresselhaus spin-orbit coupling (SOC), which supports Majorana fermions when subject to a Zeeman magnetic field and in the proximity of a superconductor. Using both analytical and numerical techniques we calculate the electronic spin texture of the Majorana end states. We find that the spin polarization of these states depends on the relative magnitude of the Rashba and Dresselhaus SOC components. Moreover, we define and calculate a local "Majorana polarization" and "Majorana density" and argue that they can be used as order parameters to characterize the topological transition between the trivial system and the system exhibiting Majorana bound modes. We find that the local Majorana polarization is correlated to the transverse spin polarization, and we propose to test the presence of Majorana fermions in a 1D system by a spin-polarized density of states measurement.