12,536 research outputs found
Side-jumps in the spin-Hall effect: construction of the Boltzmann collision integral
We present a systematic derivation of the side-jump contribution to the
spin-Hall current in systems without band structure spin-orbit interactions,
focusing on the construction of the collision integral for the Boltzmann
equation. Starting from the quantum Liouville equation for the density operator
we derive an equation describing the dynamics of the density matrix in the
first Born approximation and to first order in the driving electric field.
Elastic scattering requires conservation of the total energy, including the
spin-orbit interaction energy with the electric field: this results in a first
correction to the customary collision integral found in the Born approximation.
A second correction is due to the change in the carrier position during
collisions. It stems from the part of the density matrix off-diagonal in wave
vector. The two corrections to the collision integral add up and are
responsible for the total side-jump contribution to the spin-Hall current. The
spin-orbit-induced correction to the velocity operator also contains terms
diagonal and off-diagonal in momentum space, which together involve the total
force acting on the system. This force is explicitly shown to vanish (on the
average) in the steady state: thus the total contribution to the spin-Hall
current due to the additional terms in the velocity operator is zero.Comment: Added references, expanded discussion, revised introductio
Spin relaxation in an InAs quantum dot in the presence of terahertz driving fields
The spin relaxation in a 1D InAs quantum dot with the Rashba spin-orbit
coupling under driving THz magnetic fields is investigated by developing the
kinetic equation with the help of the Floquet-Markov theory, which is
generalized to the system with the spin-orbit coupling, to include both the
strong driving field and the electron-phonon scattering. The spin relaxation
time can be effectively prolonged or shortened by the terahertz magnetic field
depending on the frequency and strength of the terahertz magnetic field. The
effect can be understood as the sideband-modulated spin-phonon scattering. This
offers an additional way to manipulate the spin relaxation time.Comment: 8 pages, 1 figure, to be published in PR
Anomalous Rashba spin splitting in two-dimensional hole systems
It has long been assumed that the inversion asymmetry-induced Rashba spin
splitting in two-dimensional (2D) systems at zero magnetic field is
proportional to the electric field that characterizes the inversion asymmetry
of the confining potential. Here we demonstrate, both theoretically and
experimentally, that 2D heavy hole systems in accumulation layer-like single
heterostructures show the opposite behavior, i.e., a decreasing, but nonzero
electric field results in an increasing Rashba coefficient.Comment: 4 pages, 3 figure
First results of observations of transient pulsar SAXJ2103.5+4545 with the INTEGRAL observatory
We present preliminary results of observations of X-ray pulsar SAX
J2103.5+4545 with INTEGRAL observatory in Dec 2002. Maps of this sky region in
energy bands 3-10, 15-40, 40-100 and 100-200 keV are presented. The source is
significantly detected up to energies of keV. The hard X-ray flux in
the 15-100 energy band is variable, that could be connected with the orbital
phase of the binary system. We roughly reconstructed the source spectrum using
its comparison to that of Crab nebula. It is shown that the parameters of the
source spectrum in 18-150 keV energy range are compatible with that obtained
earlier by RXTE observatoryComment: 5 pages, 4 figures, accepted for publication in the Astronomy Letter
Electron spin orientation under in-plane optical excitation in GaAs quantum wells
We study the optical orientation of electron spins in GaAs/AlGaAs quantum
wells for excitation in the growth direction and for in-plane excitation. Time-
and polarization-resolved photoluminescence excitation measurements show, for
resonant excitation of the heavy-hole conduction band transition, a negligible
degree of electron spin polarization for in-plane excitation and nearly 100%
for excitation in the growth direction. For resonant excitation of the
light-hole conduction band transition, the excited electron spin polarization
has the same (opposite) direction for in-plane excitation (in the growth
direction) as for excitation into the continuum. The experimental results are
well explained by an accurate multiband theory of excitonic absorption taking
fully into account electron-hole Coulomb correlations and heavy-hole light-hole
coupling.Comment: 10 pages, 4 figures, final versio
Direct Measurement of Neutron-Star Recoil in the Oxygen-Rich Supernova Remnant Puppis A
A sequence of three Chandra X-ray Observatory High Resolution Camera images
taken over a span of five years reveals arc-second-scale displacement of RX
J0822-4300, the stellar remnant (presumably a neutron star) near the center of
the Puppis A supernova remnant. We measure its proper motion to be
0.165+/-0.025 arcsec/yr toward the west-southwest. At a distance of 2 kpc, this
corresponds to a transverse space velocity of ~1600 km/s. The space velocity is
consistent with the explosion center inferred from proper motions of the
oxygen-rich optical filaments, and confirms the idea that Puppis A resulted
from an asymmetric explosion accompanied by a kick that imparted roughly
3*10^49 ergs of kinetic energy (some 3 percent of the kinetic energy for a
typical supernova) to the stellar remnant. We discuss constraints on
core-collapse supernova models that have been proposed to explain neutron star
kick velocities
First Detection of Near-Infrared Intraday Variations in the Seyfert 1 Nucleus NGC4395
We carried out a one-night optical V and near-infrared JHK monitoring
observation of the least luminous Seyfert 1 galaxy, NGC4395, on 2004 May 1, and
detected for the first time the intraday flux variations in the J and H bands,
while such variation was not clearly seen for the K band. The detected J and H
variations are synchronized with the flux variation in the V band, which
indicates that the intraday-variable component of near-infrared continuum
emission of the NGC4395 nucleus is an extension of power-law continuum emission
to the near-infrared and originates in an outer region of the central accretion
disk. On the other hand, from our regular program of long-term optical BVI and
near-infrared JHK monitoring observation of NGC4395 from 2004 February 12 until
2005 January 22, we found large flux variations in all the bands on time scales
of days to months. The optical BVI variations are almost synchronized with each
other, but not completely with the near-infrared JHK variations. The color
temperature of the near-infrared variable component is estimated to be
T=1320-1710 K, in agreement with thermal emission from hot dust tori in active
galactic nuclei (AGNs). We therefore conclude that the near-infrared variation
consists of two components having different time scales, so that a small K-flux
variation on a time scale of a few hours would possibly be veiled by large
variation of thermal dust emission on a time scale of days.Comment: 4 pages including figures, accepted for publication in ApJ
The Effect of Spin Splitting on the Metallic Behavior of a Two-Dimensional System
Experiments on a constant-density two-dimensional hole system in a GaAs
quantum well reveal that the metallic behavior observed in the
zero-magnetic-field temperature dependence of the resistivity depends on the
symmetry of the confinement potential and the resulting spin-splitting of the
valence band
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