648 research outputs found
Transport in Luttinger Liquids
We give a brief introduction to Luttinger liquids and to the phenomena of
electronic transport or conductance in quantum wires. We explain why the
subject of transport in Luttinger liquids is relevant and fascinating and
review some important results on tunneling through barriers in a
one-dimensional quantum wire and the phenomena of persistent currents in
mesoscopic rings. We give a brief description of our own work on transport
through doubly-crossed Luttinger liquids and transport in the Schulz-Shastry
exactly solvable Luttinger-like model.Comment: Latex file, 15 pages, four eps figure
Violation of the Luttinger sum rule within the Hubbard model on a triangular lattice
The frequency-moment expansion method is developed to analyze the validity of
the Luttinger sum rule within the Mott-Hubbard insulator, as represented by the
generalized Hubbard model at half filling and large . For the particular
case of the Hubbard model with nearest-neighbor hopping on a triangular lattice
lacking the particle-hole symmetry results reveal substantial violation of the
sum rule.Comment: 4 pages, 2 figure
Magnitude and crystalline anisotropy of hole magnetization in (Ga,Mn)As
Theory of hole magnetization Mc in zinc-blende diluted ferromagnetic
semiconductors is developed relaxing the spherical approximation of earlier
approaches. The theory is employed to determine Mc for (Ga,Mn)As over a wide
range of hole concentrations and a number of crystallographic orientations of
Mn magnetization. It is found that anisotropy of Mc is practically negligible
but the obtained magnitude of Mc is significantly greater than that determined
in the spherical approximation. Its sign and value compares favorably with the
results of available magnetization measurements and ferromagnetic resonance
studies.Comment: 5 pages, 3 figure
Bose-Fermi Mixtures in One Dimension
We analyze the phase stability and the response of a mixture of bosons and
spin-polarized fermions in one dimension (1D). Unlike in 3D, phase separation
happens for low fermion densities. The dynamics of the mixture at low energy is
independent of the spin-statistics of the components, and zero-sound-like modes
exist that are essentially undamped.Comment: 5 pages; 1 figur
A Non-equilibrium STM model for Kondo Resonance on surface
Based on a no-equilibrium STM model, we study Kondo resonance on a surface by
self-consistent calculations. The shapes of tunneling spectra are dependent on
the energy range of tunneling electrons. Our results show that both
energy-cutoff and energy-window of tunneling electrons have significant
influence on the shapes of tunneling spectra. If no energy-cutoff is used, the
Kondo resonances in tunneling spectrum are peaks with the same shapes in the
density of state of absorbed magnetic atoms. This is just the prediction of
Tersoff theory. If we use an energy cutoff to remove high-energy lectrons, a
dip structure will modulate the Kondo resonance peak in the tunneling spectrum.
The real shape of Kondo peak is the mixing of the peak and dip, the so-called
Fano line shape. The method of self-consistent non-equilibrium matrix Green
function is discussed in details.Comment: 11 pages and 8 eps figur
Bosonization of Fermi liquids
We bosonize a Fermi liquid in any number of dimensions in the limit of long
wavelengths. From the bosons we construct a set of coherent states which are
related with the displacement of the Fermi surface due to particle-hole
excitations. We show that an interacting hamiltonian in terms of the original
fermions is quadratic in the bosons. We obtain a path integral representation
for the generating functional which in real time, in the semiclassical limit,
gives the Landau equation for sound waves and in the imaginary time gives us
the correct form of the specific heat for a Fermi liquid even with the
corrections due to the interactions between the fermions. We also discuss the
similarities between our results and the physics of quantum crystals.Comment: 42 pages, RevteX, preprint UIUC (1993
Evaluation of the optical conductivity tensor in terms of contour integrations
For the case of finite life-time broadening the standard Kubo-formula for the
optical conductivity tensor is rederived in terms of Green's functions by using
contour integrations, whereby finite temperatures are accounted for by using
the Fermi-Dirac distribution function. For zero life-time broadening, the
present formalism is related to expressions well-known in the literature.
Numerical aspects of how to calculate the corresponding contour integrals are
also outlined.Comment: 8 pages, Latex + 2 figure (Encapsulated Postscript
Peculiar from-Edge-to-Interior Spin Freezing in a Magnetic Dipolar Cube
By molecular dynamics simulation, we have investigated classical Heisenberg
spins, which are arrayed on a finite simple cubic lattice and interact with
each other only by the dipole-dipole interaction, and have found its peculiar
it from-Edge-to-interior freezing process. As the temperature is decreased,
spins on each edge predominantly start to freeze in a ferromagnetic alignment
parallel to the edge around the corresponding bulk transition temperature, then
from each edges grow domains with short-range orders similar to the
corresponding bulk orders, and the system ends up with a unique multi-domain
ground state at the lowest temperature. We interpret this freezing
characteristics is attributed to the anisotropic and long-range nature of the
dipole-dipole interaction combined with a finite-size effect.Comment: 11 pages 5 figure
Numerically improved computational scheme for the optical conductivity tensor in layered systems
The contour integration technique applied to calculate the optical
conductivity tensor at finite temperatures in the case of layered systems
within the framework of the spin-polarized relativistic screened
Korringa-Kohn-Rostoker band structure method is improved from the computational
point of view by applying the Gauss-Konrod quadrature for the integrals along
the different parts of the contour and by designing a cumulative special points
scheme for two-dimensional Brillouin zone integrals corresponding to cubic
systems.Comment: 17 pages, LaTeX + 4 figures (Encapsulated PostScript), submitted to
J. Phys.: Condensed Matter (19 Sept. 2000
A Solvable Model of Interacting Fermions in Two Dimensions
We introduce and study an exactly solvable model of several species of
fermions in which particles interact pairwise through a mutual magnetic field;
the interaction operates only between particles belonging to different species.
After an unitary transformation, the model reduces to one in which each
particle sees a magnetic field which depends on the total numbers of particles
of all the other species; this may be viewed as the mean-field model for a
class of anyonic theories. Our model is invariant under charge conjugation C
and the product PT (parity and time reversal). For the special case of two
species, we examine various properties of this system, such as the Hall
conductivity, the wave function overlap arising from the transfer of one
particle from one species to another, and the one-particle off-diagonal density
matrix. Our model is a generalization of a recently introduced solvable model
in one dimension.Comment: Revtex, 7 page
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