1,072 research outputs found
General Localization Lengths for Two Interacting Particles in a Disordered Chain
The propagation of an interacting particle pair in a disordered chain is
characterized by a set of localization lengths which we define. The
localization lengths are computed by a new decimation algorithm and provide a
more comprehensive picture of the two-particle propagation. We find that the
interaction delocalizes predominantly the center-of-mass motion of the pair and
use our approach to propose a consistent interpretation of the discrepancies
between previous numerical results.Comment: 4 pages, 2 epsi figure
Chaos and Interacting Electrons in Ballistic Quantum Dots
We show that the classical dynamics of independent particles can determine
the quantum properties of interacting electrons in the ballistic regime. This
connection is established using diagrammatic perturbation theory and
semiclassical finite-temperature Green functions. Specifically, the orbital
magnetism is greatly enhanced over the Landau susceptibility by the combined
effects of interactions and finite size. The presence of families of periodic
orbits in regular systems makes their susceptibility parametrically larger than
that of chaotic systems, a difference which emerges from correlation terms.Comment: 4 pages, revtex, includes 3 postscript fig
Semiclassical Approach to Orbital Magnetism of Interacting Diffusive Quantum Systems
We study interaction effects on the orbital magnetism of diffusive mesoscopic
quantum systems. By combining many-body perturbation theory with semiclassical
techniques, we show that the interaction contribution to the ensemble averaged
quantum thermodynamic potential can be reduced to an essentially classical
operator. We compute the magnetic response of disordered rings and dots for
diffusive classical dynamics. Our semiclassical approach reproduces the results
of previous diagrammatic quantum calculations.Comment: 8 pages, revtex, includes 1 postscript fi
Current-induced nonequilibrium vibrations in single-molecule devices
Finite-bias electron transport through single molecules generally induces
nonequilibrium molecular vibrations (phonons). By a mapping to a Fokker-Planck
equation, we obtain analytical scaling forms for the nonequilibrium phonon
distribution in the limit of weak electron-phonon coupling within a
minimal model. Remarkably, the width of the phonon distribution diverges as
when the coupling decreases, with voltage-dependent,
non-integer exponents . This implies a breakdown of perturbation theory
in the electron-phonon coupling for fully developed nonequilibrium. We also
discuss possible experimental implications of this result such as
current-induced dissociation of molecules.Comment: 7 pages, 4 figures; revised and extended version published in Phys.
Rev.
Localization Properties of Two Interacting Electrons in a Disordered Quasi One-Dimensional Potential
We study the transport properties of two electrons in a quasi one-dimensional
disordered wire. The electrons are subject to both, a disorder potential and a
short range two-body interaction. Using the approach developed by Iida et al. [
Ann. Phys. (N.Y.) 200 (1990) 219 ], the supersymmetry technique, and a suitable
truncation of Hilbert space, we work out the two-point correlation function in
the framework of a non-linear sigma model. We study the loop corrections to
arbitrary order. We obtain a remarkably simple and physically transparent
expression for the change of the localization length caused by the two-body
interaction.Comment: 10 page
Level Statistics and Localization for Two Interacting Particles in a Random Potential
We consider two particles with a local interaction in a random potential
at a scale (the one particle localization length). A simplified
description is provided by a Gaussian matrix ensemble with a preferential
basis. We define the symmetry breaking parameter
associated to the statistical invariance under change of basis. We show that
the Wigner-Dyson rigidity of the energy levels is maintained up to an energy
. We find that when (the
inverse lifetime of the states of the preferential basis) is smaller than
(the level spacing), and when . This implies that the two-particle localization length first
increases as before eventually behaving as .Comment: 4 pages REVTEX, 4 Figures EPS, UUENCODE
Interaction-Induced Magnetization of the Two-Dimensional Electron Gas
We consider the contribution of electron-electron interactions to the orbital
magnetization of a two-dimensional electron gas, focusing on the ballistic
limit in the regime of negligible Landau-level spacing. This regime can be
described by combining diagrammatic perturbation theory with semiclassical
techniques. At sufficiently low temperatures, the interaction-induced
magnetization overwhelms the Landau and Pauli contributions. Curiously, the
interaction-induced magnetization is third-order in the (renormalized) Coulomb
interaction. We give a simple interpretation of this effect in terms of
classical paths using a renormalization argument: a polygon must have at least
three sides in order to enclose area. To leading order in the renormalized
interaction, the renormalization argument gives exactly the same result as the
full treatment.Comment: 11 pages including 4 ps figures; uses revtex and epsf.st
Effect of noise for two interacting particles in a random potential
We investigated the effect of noise on propagation of two interacting
particles pairs in a quasi one--dimensional random potential. It is shown that
pair diffusion is strongly enhanced by short range interaction comparing with
the non--interacting case.Comment: 8 Latex pages + 3 postscript figures uu- compressed submitted to
Europhysics Letter
Flexural phonons in free-standing graphene
Rotation and reflection symmetries impose that out-of-plane (flexural)
phonons of free-standing graphene membranes have a quadratic dispersion at long
wavelength and can be excited by charge carriers in pairs only. As a result, we
find that flexural phonons dominate the phonon contribution to the resistivity
below a crossover temperature T_x where we obtain an anomalous
temperature dependence . The logarithmic factor
arises from renormalizations of the flexural phonon dispersion due to coupling
between bending and stretching degrees of freedom of the membrane.Comment: 4 pages, 2 figure
Thermopower of Single-Molecule Devices
We investigate the thermopower of single molecules weakly coupled to metallic
leads. We model the molecule in terms of the relevant electronic orbitals
coupled to phonons corresponding to both internal vibrations and to
oscillations of the molecule as a whole. The thermopower is computed by means
of rate equations including both sequential-tunneling and cotunneling
processes. Under certain conditions, the thermopower allows one to access the
electronic and phononic excitation spectrum of the molecule in a
linear-response measurement. In particular, we find that the phonon features
are more pronounced for weak lead-molecule coupling. This way of measuring the
excitation spectrum is less invasive than the more conventional current-voltage
characteristic, which, by contrast, probes the system far from equilibrium.Comment: 13 pages, 7 figures included; minor changes, version published in PR
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