1,829 research outputs found
Ab-initio Prediction of Conduction Band Spin Splitting in Zincblende Semiconductors
We use a recently developed self-consistent approximation to present
systematic \emph{ab initio} calculations of the conduction band spin splitting
in III-V and II-V zincblende semiconductors. The spin orbit interaction is
taken into account as a perturbation to the scalar relativistic hamiltonian.
These are the first calculations of conduction band spin splittings based on a
quasiparticle approach; and because the self-consistent scheme accurately
reproduces the relevant band parameters, it is expected to be a reliable
predictor of spin splittings. The results are compared to the few available
experimental data and a previous calculation based on a model one-particle
potential. We also briefly address the widely used {\bf k}{\bf p}
parameterization in the context of these results.Comment: 9 pages, 1 figur
GW method applied to localized 4f electron systems
We apply a recently developed quasiparticle self-consistent method
(QSGW) to Gd, Er, EuN, GdN, ErAs, YbN and GdAs. We show that QSGW combines
advantages separately found in conventional and LDA+ theory, in a
simple and fully \emph{ab initio} way. \qsgw reproduces the experimental
occupied levels well, though unoccupied levels are systematically
overestimated. Properties of the Fermi surface responsible for electronic
properties are in good agreement with available experimental data. GdN is
predicted to be very near a critical point of a first-order metal-insulator
transition.Comment: 5 pages,3 figures, 2 table
Spin wave dispersion based on the quasiparticle self-consistent method: NiO, MnO and -MnAs
We present spin wave dispersions in MnO, NiO, and -MnAs based on the
quasiparticle self-consistent method (\qsgw), which determines an optimum
quasiparticle picture. For MnO and NiO, \qsgw results are in rather good
agreement with experiments, in contrast to the LDA and LDA+U description. For
-MnAs, we find a collinear ferromagnetic ground state in \qsgw, while
this phase is unstable in the LDA.Comment: V2: add another figure for SW life time. Formalism is detaile
Hydrodynamic limit for weakly asymmetric simple exclusion processes in crystal lattices
We investigate the hydrodynamic limit for weakly asymmetric simple exclusion
processes in crystal lattices. We construct a suitable scaling limit by using a
discrete harmonic map. As we shall observe, the quasi-linear parabolic equation
in the limit is defined on a flat torus and depends on both the local structure
of the crystal lattice and the discrete harmonic map. We formulate the local
ergodic theorem on the crystal lattice by introducing the notion of local
function bundle, which is a family of local functions on the configuration
space. The ideas and methods are taken from the discrete geometric analysis to
these problems. Results we obtain are extensions of ones by Kipnis, Olla and
Varadhan to crystal lattices.Comment: 41 pages, 7 figure
Crystal growth and in-plane optical properties of TlBaCaCuO (n=1,2,3) superconductors
Single crystals of thallium-based cuprates with the general formula
TlBaCaCuO(n=1,2,3) have been grown by the flux
method. The superconducting transition temperatures determined by the ac
magnetic susceptibility are 92 K, 109 K, and 119 K for n=1,2,3 respectively.
X-ray diffraction measurements and EDX compositional analysis were described.
We measured in-plane optical reflectance from room temperature down to 10 K,
placing emphasis on Tl-2223. The reflectance roughly has a linear-frequency
dependence above superconducting transition temperature, but displays a
pronounced knee structure together with a dip-like feature at higher frequency
below T. Correspondingly, the ratio of the reflectances below and above
T displays a maximum and a minimum near those feature frequencies. In
particular, those features in Tl2223 appear at higher energy scale than Tl2212,
and Tl2201. The optical data are analyzed in terms of spectral function. We
discussed the physical consequences of the data in terms of both clean and
dirty limit.Comment: 8 pages, 13 figures, to be published in Phys. Rev.
Electronic structure investigation of CeB6 by means of soft X-ray scattering
The electronic structure of the heavy fermion compound CeB6 is probed by
resonant inelastic soft X-ray scattering using photon energies across the Ce 3d
and 4d absorption edges. The hybridization between the localized 4f orbitals
and the delocalized valence-band states is studied by identifying the different
spectral contributions from inelastic Raman scattering and normal fluorescence.
Pronounced energy-loss structures are observed below the elastic peak at both
the 3d and 4d thresholds. The origin and character of the inelastic scattering
structures are discussed in terms of charge-transfer excitations in connection
to the dipole allowed transitions with 4f character. Calculations within the
single impurity Anderson model with full multiplet effects are found to yield
consistent spectral functions to the experimental data.Comment: 9 pages, 4 figures, 1 table,
http://link.aps.org/doi/10.1103/PhysRevB.63.07510
Many-body Electronic Structure of Metallic alpha-Uranium
We present results for the electronic structure of alpha uranium using a
recently developed quasiparticle self-consistent GW method (QSGW). This is the
first time that the f-orbital electron-electron interactions in an actinide has
been treated by a first-principles method beyond the level of the generalized
gradient approximation (GGA) to the local density approximation (LDA). We show
that the QSGW approximation predicts an f-level shift upwards of about 0.5 eV
with respect to the other metallic s-d states and that there is a significant
f-band narrowing when compared to LDA band-structure results. Nonetheless,
because of the overall low f-electron occupation number in uranium,
ground-state properties and the occupied band structure around the Fermi energy
is not significantly affected. The correlations predominate in the unoccupied
part of the f states. This provides the first formal justification for the
success of LDA and GGA calculations in describing the ground-state properties
of this material.Comment: 4 pages, 3 fihgure
Strain-Induced Conduction Band Spin Splitting in GaAs from First Principles Calculations
We use a recently developed self-consistent GW approximation to present first
principles calculations of the conduction band spin splitting in GaAs under
[110] strain. The spin orbit interaction is taken into account as a
perturbation to the scalar relativistic hamiltonian. These are the first
calculations of conduction band spin splitting under deformation based on a
quasiparticle approach; and because the self-consistent GW scheme accurately
reproduces the relevant band parameters, it is expected to be a reliable
predictor of spin splittings. We also discuss the spin relaxation time under
[110] strain and show that it exhibits an in-plane anisotropy, which can be
exploited to obtain the magnitude and sign of the conduction band spin
splitting experimentally.Comment: 8 pages, 4 figures, 1 tabl
A Massive Jet Ejection Event from the Microquasar SS 433 Accompanying Rapid X-Ray Variability
Microquasars occasionally exhibit massive jet ejections which are distinct
from the continuous or quasi-continuous weak jet ejections. Because those
massive jet ejections are rare and short events, they have hardly been observed
in X-ray so far. In this paper, the first X-ray observation of a massive jet
ejection from the microquasar SS 433 with the Rossi X-ray Timing Explorer
(RXTE) is reported. SS 433 undergoing a massive ejection event shows a variety
of new phenomena including a QPO-like feature near 0.1 Hz, rapid time
variability, and shot-like activities. The shot-like activity may be caused by
the formation of a small plasma bullet. A massive jet may be consist of
thousands of those plasma bullets ejected from the binary system. The size,
mass, internal energy, and kinetic energy of the bullets and the massive jet
are estimated.Comment: 21 pages including 5 figures, submitted to Ap
- âŠ