Searcharxiv⌕ Search

arXiv subjects

N. A. Sinitsyn

Publications and source records attributed to N. A. Sinitsyn.

66 records · Page 4Linked to original sources
arXiv2005

Dependence of the intrinsic spin Hall effect on spin-orbit interaction character

We report on a comparative numerical study of the spin Hall conductivity in two-dimensions for three different spin-orbit interaction models; the standard k-linear Rashba model, the k-cubic Rashba model that describes two-dimensional hole systems, and a modified k-linear Rashba model in which the spin-orbit coupling strength is energy dependent. Numerical finite-size Kubo formula results indicate that the spin Hall conductivity of the k-linear Rashba model vanishes for frequency $ω$ much smaller than the scattering rate $τ^{-1}$, with order one relative fluctuations surviving out to large system sizes. For the k-cubic Rashba model case, the spin Hall conductivity does not depend noticeably on $ωτ$ and is finite in the {\em dc} limit, in agreement with experiment. For the modified k-linear Rashba model the spin Hall conductivity is noticeably $ωτ$ dependent but approaches a finite value in the {\em dc} limit. We discuss these results in the light of a spectral decomposition of the spin Hall conductivity and associated sum rules, and in relation to a proposed separation of the spin Hall conductivity into skew-scattering, intrinsic, and interband vertex correction contributions.

cond-mat.mes-hall↗
arXiv2004

Semiclassical theory of spin transport in spin-orbit coupled systems

Motivated by recent interest in novel spintronics effects, we develop a semiclassical theory of spin transport that is valid for spin-orbit coupled bands. Aside from the obvious convective term in which the average spin is transported at the wavepacket group velocity, the spin current has additional contributions from the wavepacket's spin and torque dipole moments. Electric field corrections to the group velocity and carrier spin contribute to the convective term. Summing all terms we obtain an expression for the intrinsic spin-Hall conductivity of a hole-doped semiconductor, which agrees with the Kubo formula prediction for the same quantity. We discuss the calculation of spin accumulation, which illustrates the importance of the torque dipole near the boundary of the system.

cond-mat.mes-hall↗
arXiv2004

Universal Intrinsic Spin-Hall Effect

We describe a new effect in semiconductor spintronics that leads to dissipationless spin-currents in paramagnetic spin-orbit coupled systems. We argue that in a high mobility two-dimensional electron system with substantial Rashba spin-orbit coupling, a spin-current that flows perpendicular to the charge current is intrinsic. In the usual case where both spin-orbit split bands are occupied, the spin-Hall conductivity has a universal value.

cond-mat.mes-hall↗
arXiv2003

Spin-Hall and spin-diagonal conductivity in the presence of Rashba and Dresselhaus spin-orbit coupling

We investigate the spin-current linear response conductivity tensor to an electric field in a paramagnetic two dimensonal electron gas with both Rashba and Dresselhaus spin-orbit coupling in the weak scattering regime. In the ususal case where both spin-orbit-split bands are occupied, we find that the spin-Hall conductivity depends only on the sign of the difference in magnitude of the Rashba and Dresselhaus coupling strengths except within a narrow window where both coupling strengths are equal. We also find a new effect in which a spin current is generated in the direction of the driving field whenever the Dresselhaus spin-orbit coupling is nonzero. We discuss experimental implications of this finding taking into account the finite mobility and typical parameters of current samples and possible experimental set ups for its detection.

cond-mat.mes-hall↗
arXiv2003

Spin transitions in time-dependent regular and random magnetic fields

We study the transition between Zeeman levels of an arbitrary spin placed into a regular time-dependent field and a random field with the Gaussian distribution. One component of the regular field changes its sign at some moment of time, whereas another component does not change substantially. The noise is assumed to be fast. In this assumption we find analytically the ensemble average of the spin density matrix and its fluctuations.

quant-ph↗
arXiv2003

Fast noise in the Landau-Zener theory

We study the influence of a fast noise on Landau-Zener transitions. We demonstrate that a fast colored noise much weaker than the conventional white noise can produce transitions itself or can change substantially the Landau-Zener transition probabilities. In the limit of fast colored or strong white noise we derive asymptotically exact formulae for transition probabilities and study the time evolution of a spin coupled to the noise and a sweeping magnetic field.

cond-mat.mes-hall↗
arXiv2002

Multiparticle Landau-Zener problem

We propose a simple ansatz that allows to generate new exactly solvable multi-state Landau-Zener models. It is based on a system of two decoupled two-level atoms whose levels vary with time and cross at some moments. Then we consider multiparticle systems with Heisenberg equations for annihilation operators having similar structure with Shrödinger equation for amplitudes in multistate Landau-Zener models and show that the corresponding Shrödinger equation in multiparticle sector belongs to the multistate Landau-Zener class. This observation allows to generate new exactly solvable models from already known ones. We discuss possible applications of the new solutions in the problem of the driven charge transport in quantum dots.

cond-mat.mes-hall↗
arXiv2001

Landau-Zener transitions in a linear chain

We present an exact asymptotic solution for electron transition amplitudes in an infinite linear chain driven by an external homogeneous time-dependent electric field. This solution extends the Landau-Zener theory for the case of infinite number of states in discrete spectrum. In addition to transition amplitudes we calculate an effective diffusion constant.

cond-mat.mes-hall↗
arXiv2001

Formation of Two Component Bose Condensate During the Chemical Potential Curve Crossing

In this article we study the formation of the two modes Bose-Einstein condensate and the correlation between them. We show that beyond the mean field approximation the dissociation of a molecular condensate due to the chemical potential curve crossing leads to the formation of two modes condensate. We also show that these two modes are correlated in a two mode squeezed state.

cond-mat.stat-mech↗
arXiv2001

Molecular nanomagnets in ac magnetic field

The behavior of molecular nanomagnets in periodic magnetic field transverse to the easy axis direction is investigated. It is shown that at sufficiently strong field the tunneling time can be considerably reduced.

cond-mat.mes-hall↗
arXiv2000

On the generalized Landau-Zener problem

During the adiabatic time evolution levels crossing violates the adiabaticity and makes transitions between levels possible. Conventionally only two energy levels cross simultaneously. The transition probabilities for this case were found by Landau and Zener. However, the multilevel crossing happens systematically rather than occasionally if the Hamiltonian possesses a special symmetry. The simplest physical realization of the multilevel crossing are the Zeeman multiplet in a varying magnetic field and an electron in one-dimensional chain driven by the time-dependent electric field. We present asymptotics of the transition amplitudes for these kinds of the multilevel crossing. They are based on an exact solution for a model n-state, time-dependent Schrödinger equation.

cond-mat.str-el↗