2,974 research outputs found
The glass transition and the Coulomb gap in electron glasses
We establish the connection between the presence of a glass phase and the
appearance of a Coulomb gap in disordered materials with strongly interacting
electrons. Treating multiparticle correlations in a systematic way, we show
that in the case of strong disorder a continuous glass transition takes place
whose Landau expansion is identical to that of the Sherrington-Kirkpatrick spin
glass. We show that the marginal stability of the glass phase controls the
physics of these systems: it results in slow dynamics and leads to the
formation of a Coulomb gap
Dielectric susceptibility of the Coulomb-glass
We derive a microscopic expression for the dielectric susceptibility
of a Coulomb glass, which corresponds to the definition used in classical
electrodynamics, the derivative of the polarization with respect to the
electric field. The fluctuation-dissipation theorem tells us that is a
function of the thermal fluctuations of the dipole moment of the system. We
calculate numerically for three-dimensional Coulomb glasses as a
function of temperature and frequency
Off-equilibrium dynamics of the two-dimensional Coulomb glass
The dynamics of the 2D Coulomb glass model is investigated by kinetic Monte
Carlo simulation. An exponential divergence of the relaxation time signals a
zero-temperature freezing transition. At low temperatures the dynamics of the
system is glassy. The local charge correlations and the response to
perturbations of the local potential show aging. The dynamics of formation of
the Coulomb gap is slow and the density of states at the Fermi level decays in
time as a power law. The relevance of these findings for recent transport
experiments in Anderson-insulating films is pointed out.Comment: 7 pages, 7 figure
Monte-Carlo Simulations of the Dynamical Behavior of the Coulomb Glass
We study the dynamical behavior of disordered many-particle systems with
long-range Coulomb interactions by means of damage-spreading simulations. In
this type of Monte-Carlo simulations one investigates the time evolution of the
damage, i.e. the difference of the occupation numbers of two systems, subjected
to the same thermal noise. We analyze the dependence of the damage on
temperature and disorder strength. For zero disorder the spreading transition
coincides with the equilibrium phase transition, whereas for finite disorder,
we find evidence for a dynamical phase transition well below the transition
temperature of the pure system.Comment: 10 pages RevTeX, 8 Postscript figure
Universal Crossover between Efros-Shklovskii and Mott Variable-Range-Hopping Regimes
A universal scaling function, describing the crossover between the Mott and
the Efros-Shklovskii hopping regimes, is derived, using the percolation picture
of transport in strongly localized systems. This function is agrees very well
with experimental data. Quantitative comparison with experiment allows for the
possible determination of the role played by polarons in the transport.Comment: 7 pages + 1 figure, Revte
Coherent State Path Integrals in the Weyl Representation
We construct a representation of the coherent state path integral using the
Weyl symbol of the Hamiltonian operator. This representation is very different
from the usual path integral forms suggested by Klauder and Skagerstan in
\cite{Klau85}, which involve the normal or the antinormal ordering of the
Hamiltonian. These different representations, although equivalent quantum
mechanically, lead to different semiclassical limits. We show that the
semiclassical limit of the coherent state propagator in Weyl representation is
involves classical trajectories that are independent on the coherent states
width. This propagator is also free from the phase corrections found in
\cite{Bar01} for the two Klauder forms and provides an explicit connection
between the Wigner and the Husimi representations of the evolution operator.Comment: 23 page
The Electron Glass in a Switchable Mirror: Relaxation, Aging and Universality
The rare earth hydride YH can be tuned through the
metal-insulator transition both by changing and by illumination with
ultraviolet light. The transition is dominated by strong electron-electron
interactions, with transport in the insulator sensitive to both a Coulomb gap
and persistent quantum fluctuations. Via a systematic variation of UV
illumination time, photon flux, Coulomb gap depth, and temperature, we
demonstrate that polycrystalline YH serves as a model system for
studying the properties of the interacting electron glass. Prominent among its
features are logarithmic relaxation, aging, and universal scaling of the
conductivity
Electronic correlation effects and the Coulomb gap at finite temperature
We have investigated the effect of the long-range Coulomb interaction on the
one-particle excitation spectrum of n-type Germanium, using tunneling
spectroscopy on mechanically controllable break junctions. The tunnel
conductance was measured as a function of energy and temperature. At low
temperatures, the spectra reveal a minimum at zero bias voltage due to the
Coulomb gap. In the temperature range above 1 K the Coulomb gap is filled by
thermal excitations. This behavior is reflected in the temperature dependence
of the variable-range hopping resitivity measured on the same samples: Up to a
few degrees Kelvin the Efros-Shkovskii ln law is obeyed,
whereas at higher temperatures deviations from this law are observed,
indicating a cross-over to Mott's ln law. The mechanism of
this cross-over is different from that considered previously in the literature.Comment: 3 pages, 3 figure
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