118 research outputs found
Theory of laser-induced demagnetization at high temperatures
Laser-induced demagnetization is theoretically studied by explicitly taking
into account interactions among electrons, spins and lattice. Assuming that the
demagnetization processes take place during the thermalization of the
sub-systems, the temperature dynamics is given by the energy transfer between
the thermalized interacting baths. These energy transfers are accounted for
explicitly through electron-magnons and electron-phonons interaction, which
govern the demagnetization time scale. By properly treating the spin system in
a self-consistent random phase approximation, we derive magnetization dynamic
equations for a broad range of temperature. The dependence of demagnetization
on the temperature and pumping laser intensity is calculated in detail. In
particular, we show several salient features for understanding magnetization
dynamics near the Curie temperature. While the critical slowdown in dynamics
occurs, we find that an external magnetic field can restore the fast dynamics.
We discuss the implication of the fast dynamics in the application of heat
assisted magnetic recording.Comment: 11 Pages, 7 Figure
Spin relaxation due to random Rashba spin-orbit coupling in GaAs (110) quantum wells
We investigate the spin relaxation due to the random Rashba spin-orbit
coupling in symmetric GaAs (110) quantum wells from the fully microscopic
kinetic spin Bloch equation approach. All relevant scatterings, such as the
electron-impurity, electron--longitudinal-optical-phonon,
electron--acoustic-phonon, as well as electron-electron Coulomb scatterings are
explicitly included. It is shown that our calculation reproduces the
experimental data by M\"uller {\em et al.} [Phys. Rev. Lett. {\bf 101}, 206601
(2008)] for a reasonable choice of parameter values. We also predict that the
temperature dependence of spin relaxation time presents a peak in the case with
low impurity density, which originates from the electron-electron Coulomb
scattering.Comment: 5 pages, 2 figures, EPL in pres
Spin Orientation of Holes in Quantum Wells
This paper reviews the spin orientation of spin-3/2 holes in quantum wells.
We discuss the Zeeman and Rashba spin splitting in hole systems that are
qualitatively different from their counterparts in electron systems. We show
how a systematic understanding of the unusual spin-dependent phenomena in hole
systems can be gained using a multipole expansion of the spin density matrix.
As an example we discuss spin precession in hole systems that can give rise to
an alternating spin polarization. Finally, we discuss the qualitatively
different regimes of hole spin polarization decay in clean and dirty samples.Comment: 14 pages, 8 figure
Nucleon-nucleon potential in finite nuclei
We consider the spin-isospin-independent central part of the residual
nucleon-nucleon potential in finite spherical nuclei taking into account the
deformation effects of the nucleons within the surrounding nuclear environment.
It is shown that inside the nucleus the short-range repulsive contribution of
the potential is increased and the intermediate attraction is decreased. We
identify the growth of the radial component of the spin-isospin independent
short-range part of the in-medium nucleon-nucleon interaction as the
responsible agent that prevents the radial collapse of the nucleus.Comment: 9 pages, 3 eps figure
All-optical evaluation of spin-orbit interaction based on diffusive spin motion in a two-dimensional electron gas
A method is presented that enables the measurement of spin-orbit coefficients in a diffusive two-dimensional electron gas without the need for processing the sample structure, applying electrical currents or resolving the spatial pattern of the spin mode. It is based on the dependence of the average electron velocity on the spatial distance between local excitation and detection of spin polarization, resulting in a variation of spin precession frequency that in an external magnetic field is linear in the spatial separation. By scanning the relative positions of the exciting and probing spots in a time-resolved Kerr rotation microscope, frequency gradients along the [100] and [010] crystal axes of GaAs/AlGaAs QWs are measured to obtain the Rashba and Dresselhaus spin-orbit coefficients, α and β. This simple method can be applied in a variety of materials with electron diffusion for evaluating spin-orbit coefficients
Comment on "Spin relaxation in quantum Hall systems"
W. Apel and Yu.A. Bychkov have recently considered the spin relaxation in a
2D quantum Hall system for the filling factor close to unity [PRL v.82, 3324
(1999)]. The authors considered only one spin flip mechanism (direct
spin-phonon coupling) among several possible spin-orbit related ones and came
to the conclusion that the spin relaxation time due to this mechanism is quite
short: around s at B=10 T (for GaAs). This time is much shorter than
the typical time ( s) obtained earlier by D. Frenkel while considering
the spin relaxation of 2D electrons in a quantizing magnetic field without the
Coulomb interaction and for the same spin-phonon coupling. I show that the
authors' conclusion about the value of the spin-flip time is wrong and have
deduced the correct time which is by several orders of magnitude longer. I also
discuss the admixture mechanism of the spin-orbit interaction.Comment: 1 pag
Laser in the axial electric field as a tool to search for P-, T- invariance violation
We consider rotation of polarization plane of the laser light when a gas
laser is placed in a longitudinal electric field (10~kV/cm). It is shown that
residual anisotropy of the laser cavity 10^{-6} and the sensitivity to the
angle of polarization plane rotation about 10^{-11} -10^{-12} rad allows one to
measure an electron EDM with the sensitivity about 10^{-30} e cm.Comment: 12 page
Effect of nonequilibrium phonons on hot-electron spin relaxation in n-type GaAs quantum wells
We have studied the effect of nonequilibrium longitudinal optical phonons on
hot-electron spin relaxation in -type GaAs quantum wells. The longitudinal
optical phonons, due to the finite relaxation rate, are driven to
nonequilibrium states by electrons under an in-plane electric field. The
nonequilibrium phonons then in turn influence the electron spin relaxation
properties via modifying the electron heating and drifting. The spin relaxation
time is elongated due to the enhanced electron heating and thus the
electron-phonon scattering in the presence of nonequilibrium phonons. The
frequency of spin precession, which is roughly proportional to the electron
drift velocity, can be either increased (at low electric field and/or high
lattice temperature) or decreased (at high electric field and/or low lattice
temperature). The nonequilibrium phonon effect is more pronounced when the
electron density is high and the impurity density is low.Comment: 6 pages, 3 figure
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