93 research outputs found
Quantum diffusion in a random potential: A consistent perturbation theory
We scrutinize the diagrammatic perturbation theory of noninteracting
electrons in a random potential with the aim to accomplish a consistent
comprehensive theory of quantum diffusion. Ward identity between the
one-electron self-energy and the two-particle irreducible vertex is generally
not guaranteed in the perturbation theory with only elastic scatterings. We
show how the Ward identity can be established in practical approximations and
how the functions from the perturbation expansion should be used to obtain a
fully consistent conserving theory. We derive the low-energy asymptotics of the
conserving full two-particle vertex from which we find an exact representation
of the diffusion pole and of the static diffusion constant in terms of Green
functions of the perturbation expansion. We illustrate the construction on the
leading vertex corrections to the mean-field diffusion due to maximally-crossed
diagrams responsible for weak localization.Comment: 12 pages, 3 figure
A mean-field theory of Anderson localization
Anderson model of noninteracting disordered electrons is studied in high
spatial dimensions. We find that off-diagonal one- and two-particle propagators
behave as gaussian random variables w.r.t. momentum summations. With this
simplification and with the electron-hole symmetry we reduce the parquet
equations for two-particle irreducible vertices to a single algebraic equation
for a local vertex. We find a disorder-driven bifurcation point in this
equation signalling vanishing of diffusion and onset of Anderson localization.
There is no bifurcation in where all states are localized. A natural
order parameter for Anderson localization pops up in the construction.Comment: REVTeX4, 4 pages, 2 EPS figure
Electronic structure and spectral properties of Am, Cm and Bk: Charge density self-consistent LDA+HIA calculations in FP-LAPW basis
We provide a straightforward and numerically efficient procedure to perform
local density approximation + Hubbard I (LDA+HIA) calculations, including
self-consistency over the charge density, within the full potential linearized
augmented plane wave (FP-LAPW) method. This implementation is all-electron,
includes spin-orbit interaction, and makes no shape approximations for the
charge density. The method is applied to calculate selected heavy actinides in
the paramagnetic phase. The electronic structure and spectral properties of Am
and Cm metals obtained are in agreement with previous dynamical mean-field
theory (LDA+DMFT) calculations and with available experimental data. We point
out that the charge density self-consistent LDA+HIA calculations predict the
charge on Bk to exceed the atomic integer value by 0.22.Comment: 8 pages, 1 figur
Electron scattering in HCl: An improved nonlocal resonance model
We present an improved nonlocal resonance model for electron-HCl collisions. The short-range part of the model is fitted to ab initio electron-scattering eigenphase sums calculated using the Schwinger multichannel method, while the long-range part is based on the ab initio potential-energy curve of the bound anion HCl-. This model significantly improves the agreement of nonlocal resonance calculations with recent absolute experimental data on dissociative electron attachment cross sections for HCl and DCl. It also partly resolves an inconsistency in the temperature effect in dissociative electron attachment to HCl present in the literature. Finally, the present model reproduces all qualitative structures observed previously in elastic scattering and vibrational-excitation cross sections
Longitudinal conductivity and transverse charge redistribution in coupled quantum wells subject to in-plane magnetic fields
In double quantum wells electrons experience a Lorentz force oriented
perpendicular to the structure plane when an electric current is driven
perpendicular to the direction of an in-plane magnetic field. Consequently, the
excess charge is accumulated in one of the wells. The polarization of a bilayer
electron system and the corresponding Hall voltage are shown to contribute
substantially to the in-plane conductivity.Comment: 3 pages, 2 figure
Orbital magnetic moment and extrinsic spin Hall effect for iron impurity in gold
We report electronic structure calculations of an iron impurity in gold host.
The spin, orbital and dipole magnetic moments were investigated using the
LDA+ correlated band theory. We show that the {\em
around-mean-field}-LDA+ reproduces the XMCD experimental data well and does
not lead to formation of a large orbital moment on the Fe atom. Furthermore,
exact diagonalization of the multi-orbital Anderson impurity model with the
full Coulomb interaction matrix and the spin-orbit coupling is performed in
order to estimate the spin Hall angle. The obtained value suggests that there is no giant extrinsic spin Hall effect due to
scattering on iron impurities in gold.Comment: 5 pages, 2 figure
Valence-band satellite in the ferromagnetic nickel: LDA+DMFT study with exact diagonalization
The valence-band spectrum of the ferromagnetic nickel is calculated using the
LDA+DMFT method. The auxiliary impurity model emerging in the course of the
calculations is discretized and solved with the exact diagonalization, or, more
precisely, with the Lanczos method. Particular emphasis is given to spin
dependence of the valence-band satellite that is observed around 6 eV below the
Fermi level. The calculated satellite is strongly spin polarized in accord with
experimental findings.Comment: REVTeX 4, 8 pages, 5 figure
Mean-field theories for disordered electrons: Diffusion pole and Anderson localization
We discuss conditions to be put on mean-field-like theories to be able to
describe fundamental physical phenomena in disordered electron systems. In
particular, we investigate options for a consistent mean-field theory of
electron localization and for a reliable description of transport properties.
We argue that a mean-field theory for the Anderson localization transition must
be electron-hole symmetric and self-consistent at the two-particle (vertex)
level. We show that such a theory with local equations can be derived from the
asymptotic limit to high spatial dimensions. The weight of the diffusion pole,
i. e., the number of diffusive states at the Fermi energy, in this mean-field
theory decreases with the increasing disorder strength and vanishes in the
localized phase. Consequences of the disclosed behavior for our understanding
of vanishing of electron diffusion are discussed.Comment: REVTeX4, 11 pages, no figure
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