112 research outputs found
Suppression of \bbox{T_c} in superconducting amorphous wires
The suppression of the mean field temperature of the superconducting
transition, , in homogeneous amorphous wires is studied. We develop a
theory that gives in situations when the dynamically enhanced Coulomb
repulsion competes with the contact attraction. The theory accurately describes
recent experiments on --suppression in superconducting wires, after a
procedure that minimizes the role of nonuniversal mechanisms influencing
is applied.Comment: RevTeX, 4 pages, 3 figure
Renormalization group analysis of thermal transport in the disordered Fermi liquid
We present a detailed study of thermal transport in the disordered Fermi
liquid with short-range interactions. At temperatures smaller than the impurity
scattering rate, i.e., in the diffusive regime, thermal conductivity acquires
non-analytic quantum corrections. When these quantum corrections become large
at low temperatures, the calculation of thermal conductivity demands a
theoretical approach that treats disorder and interactions on an equal footing.
In this paper, we develop such an approach by merging Luttinger's idea of using
gravitational potentials for the analysis of thermal phenomena with a
renormalization group calculation based on the Keldysh nonlinear sigma model.
The gravitational potentials are introduced in the action as auxiliary sources
that couple to the heat density. These sources are a convenient tool for
generating expressions for the heat density and its correlation function from
the partition function. Already in the absence of the gravitational potentials,
the nonlinear sigma model contains several temperature-dependent
renormalization group charges. When the gravitational potentials are introduced
into the model, they acquire an independent renormalization group flow. We show
that this flow preserves the phenomenological form of the correlation function,
reflecting its relation to the specific heat and the constraints imposed by
energy conservation. The main result of our analysis is that the
Wiedemann-Franz law holds down to the lowest temperatures even in the presence
of disorder and interactions and despite the quantum corrections that arise for
both the electric and thermal conductivities.Comment: 30 pages, 37 figure
Keldysh approach to the renormalization group analysis of the disordered electron liquid
We present a Keldysh nonlinear sigma-model approach to the renormalization
group analysis of the disordered electron liquid. We include both the Coulomb
interaction and Fermi-liquid type interactions in the singlet and triplet
channels into the formalism. Based on this model, we reproduce the coupled
renormalization group equations for the diffusion coefficient, the frequency,
and interaction constants previously derived with the replica model in the
imaginary time technique. With the help of source fields coupling to the
particle-number and spin densities, we study the density-density and spin
density-spin density correlation functions in the diffusive regime. This allows
us to obtain results for the electric conductivity and the spin susceptibility
and thereby to re-derive the main results of the one-loop renormalization group
analysis of the disordered electron liquid in the Keldysh formalism.Comment: 29 pages, 15 figure
Heat diffusion in the disordered electron gas
We study the thermal conductivity of the disordered two-dimensional electron
gas. To this end we analyze the heat density-heat density correlation function
concentrating on the scattering processes induced by the Coulomb interaction in
the sub-temperature energy range. These scattering processes are at the origin
of logarithmic corrections violating the Wiedemann-Franz law. Special care is
devoted to the definition of the heat density in the presence of the long-range
Coulomb interaction. To clarify the structure of the correlation function, we
present details of a perturbative calculation. While the conservation of energy
strongly constrains the general form of the heat density-heat density
correlation function, the balance of various terms turns out to be rather
different from that for the correlation functions of other conserved quantities
such as the density-density or spin density-spin density correlation function.Comment: 23 pages, 12 figure
Kinetics of the disordered Bose gas with collisions
We discuss the kinetics of the disordered interacting Bose gas using the
Boltzmann transport equation. The theory may serve as a unifying framework for
studying questions of dynamics of the expanding Bose gas at different stages of
the expansion. We show that the transport theory allows us to straightforwardly
reproduce and generalize a number of results previously obtained from
microscopic models in different formalisms. Based on estimates for the
interparticle scattering rates, we discuss the relevance of interaction effects
for the localization problem in the interacting disordered Bose gas. We argue
that, if the number of particles is large enough, the size of the expanding
cloud may exceed the localization length. We describe the spreading of the wave
packet in this regime as collision-induced diffusion and compare the obtained
rate of expansion to known results on subdiffusive spreading in nonlinear
disordered lattices.Comment: 7 page
Thermal Transport and Wiedemann-Franz Law in the Disordered Fermi Liquid
We study thermal transport in the disordered Fermi liquid at low
temperatures. Gravitational potentials are used as sources for finding the heat
density and its correlation function. For a comprehensive study, we extend the
renormalization group (RG) analysis developed for electric transport by
including the gravitational potentials into the RG scheme. Our analysis reveals
that the Wiedemann-Franz law remains valid even in the presence of quantum
corrections caused by the interplay of diffusion modes and the electron
electron interaction. In the present scheme this fundamental relation is
closely connected with a fixed point in the multi-parametric RG-flow of the
gravitational potentials.Comment: 5 page
Inhomogeneous metallic phase upon disordering a two dimensional Mott insulator
We find that isoelectronic disorder destroys the spectral gap in a
Mott-Hubbard insulator in 2D leading, most unexpectedly, to a new metallic
phase. This phase is spatially inhomogeneous with metallic behavior coexisting
with antiferromagnetic long range order. Even though the Mott gap in the pure
system is much larger than antiferromagnetic exchange, the spectral gap is
destroyed locally in regions where the disorder potential is high enough to
overcome the inter-electron repulsion thereby generating puddles where charge
fluctuations are enhanced. With increasing disorder, these puddles expand and
concomitantly the states at the Fermi energy get extended leading to a metallic
phase. We discuss the implications of our results for experiments.Comment: (4 pages, 5 figures
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