252 research outputs found
Effect of dephasing on mesoscopic conductance fluctuations in quantum dots with single channel leads
We consider the distribution of conductance fluctuations in disordered
quantum dots with single channel leads. Using a perturbative diagrammatic
approach, valid for continuous level spectra, we describe dephasing due to
processes within the dot by considering two different contributions to the
level broadening, thus satisfying particle number conservation. Instead of a
completely non-Gaussian distribution, which occurs for zero dephasing, we find
for strong dephasing that the distribution is mainly Gaussian with
non-universal variance and non-Gaussian tails.Comment: 11 pages in REVTeX two-column format; 6 eps figures included;
submitted to Phys. Rev.
On the Four-Dimensional Diluted Ising Model
In this letter we show strong numerical evidence that the four dimensional
Diluted Ising Model for a large dilution is not described by the Mean Field
exponents. These results suggest the existence of a new fixed point with
non-gaussian exponents.Comment: 9 pages. compressed ps-file (uufiles
Interaction-tuned Anderson versus Mott localization
Disorder or sufficiently strong interactions can render a metallic state
unstable causing it to turn into an insulating one. Despite the fact that the
interplay of these two routes to a vanishing conductivity has been a central
research topic, a unifying picture has not emerged so far. Here, we establish
that the two-dimensional Falicov-Kimball model, one of the simplest lattice
models of strong electron correlation does allow for the study of this
interplay. In particular, we show that this model at particle-hole symmetry
possesses three distinct thermodynamic insulating phases and exhibits Anderson
localization. The previously reported metallic phase is identified as a
finite-size feature due to the presence of weak localization. We characterize
these phases by their electronic density of states, staggered occupation,
conductivity, and the generalized inverse participation ratio. The implications
of our findings for other strongly correlated systems are discussed.Comment: 5 pages, 4 figure
Nonequilibrium dynamical mean-field theory for bosonic lattice models
We develop the nonequilibrium extension of bosonic dynamical mean field
theory (BDMFT) and a Nambu real-time strong-coupling perturbative impurity
solver. In contrast to Gutzwiller mean-field theory and strong coupling
perturbative approaches, nonequilibrium BDMFT captures not only dynamical
transitions, but also damping and thermalization effects at finite temperature.
We apply the formalism to quenches in the Bose-Hubbard model, starting both
from the normal and Bose-condensed phases. Depending on the parameter regime,
one observes qualitatively different dynamical properties, such as rapid
thermalization, trapping in metastable superfluid or normal states, as well as
long-lived or strongly damped amplitude oscillations. We summarize our results
in non-equilibrium "phase diagrams" which map out the different dynamical
regimes.Comment: 18 pages, 8 figure
Liquid-gas phase transition at and below the critical point
This article is a continuation of our previous works (see Yukhnovskii I.R. et
al., J. Stat. Phys, 1995, 80, 405 and references therein), where we have
described the behavior of a simple system of interacting particles in the
region of temperatures at and about the critical point, T \geqslant T_{c}. Now
we present a description of the behavior of the system at the critical point
(T_{c}, \eta_{c}) and in the region below the critical point. The calculation
is carried out from the first principles. The expression for the grand
canonical partition function is brought to the functional integrals defined on
the set of collective variables. The Ising-like form is singled out. Below
T_{c}, when a gas-liquid system undergoes a phase transition of the first
order, i.e., boiling, a "jump" occurs from the "extreme" high probability gas
state to the "extreme" high probability liquid state, releasing or absorbing
the latent heat of the transition. The phase equilibria conditions are also
derived.Comment: 23 pages, 9 figure
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