14 research outputs found
Renormalization group study of a two-valley system with spin-splitting
Renormalization group equations in a two-valley system with valley-splitting
and intervalley scattering are derived in the presence of spin-splitting
induced by a parallel magnetic field. The relevant amplitudes in different
regimes set by the relative strengths of the spin and valley splittings and the
intervalley scattering rate are identified. The range of applicability of the
standard formula for the magnetoconductance is discussed
Renormalization group study of intervalley scattering and valley splitting in a two-valley system
Renormalization group equations are derived for the case when both valley
splitting and intervalley scattering are present in a two-valley system. A
third scaling parameter is shown to be relevant when the two bands are split
but otherwise distinct. The existence of this parameter changes the
quantitative behavior at finite temperatures, but the qualitative conclusions
of the two-parameter theory are shown to be unaffected for realistic choice of
parameters
Test of scaling theory in two dimensions in the presence of valley splitting and intervalley scattering in Si-MOSFETs
We show that once the effects of valley splitting and intervalley scattering
are incorporated, renormalization group theory consistently describes the
metallic phase in silicon metal-oxide-semiconductor field-effect transistors
down to the lowest accessible temperatures
Anderson localization from the replica formalism
We study Anderson localization in quasi--one--dimensional disordered wires
within the framework of the replica --model. Applying a semiclassical
approach (geodesic action plus Gaussian fluctuations) recently introduced
within the context of supersymmetry by Lamacraft, Simons and Zirnbauer
\cite{LSZ}, we compute the {\em exact} density of transmission matrix
eigenvalues of superconducting wires (of symmetry class I.) For the unitary
class of metallic systems (class ) we are able to obtain the density
function, save for its large transmission tail.Comment: 4 pages, 1 figur
Quantum kinetic approach for studying thermal transport in the presence of electron-electron interactions and disorder
A user friendly scheme based on the quantum kinetic equation is developed for
studying thermal transport phenomena in the presence of interactions and
disorder. We demonstrate that this scheme is suitable for both a systematic
perturbative calculation as well as a general analysis. We believe that we
present an adequate alternative to the Kubo formula, which for the thermal
transport is rather cumbersome.Comment: 30 pages, 16 figure
From Luttinger liquid to Altshuler-Aronov anomaly in multi-channel quantum wires
A crossover theory connecting Altshuler-Aronov electron-electron interaction
corrections and Luttinger liquid behavior in quasi-1D disordered conductors has
been formulated. Based on an interacting non-linear sigma model, we compute the
tunneling density of states and the interaction correction to the conductivity,
covering the full crossover.Comment: 15 pages, 3 figures, revised version, accepted by PR
Quantum kinetic approach to the calculation of the Nernst effect
We show that the strong Nernst effect observed recently in amorphous
superconducting films far above the critical temperature is caused by the
fluctuations of the superconducting order parameter. We employ the quantum
kinetic approach for the derivation of the Nernst coefficient. We present here
the main steps of the calculation and discuss some subtle issues that we
encountered while calculating the Nernst coefficient. In particular, we
demonstrate that in the limit T=0 the contribution of the magnetization ensures
the vanishing of the Nernst signal in accordance with the third law of
thermodynamics. We obtained a striking agreement between our theoretical
calculations and the experimental data in a broad region of temperatures and
magnetic fields.Comment: 24 pages, 13 figure
Quantum interference and Coulomb interaction in arrays of tunnel junctions
We study the electronic properties of an array of small metallic grains
connected by tunnel junctions. Such an array serves as a model for a granular
metal. Previous theoretical studies of junction arrays were based on models of
quantum dissipation which did not take into account the diffusive motion of
electrons within the grains. We demonstrate that these models break down at
sufficiently low temperatures: for a correct description of the screening
properties of a granular metal at low energies the diffusive nature of the
electronic motion within the grains is crucial. We present both a diagrammatic
and a functional integral approach to analyse the properties of junction
arrays. In particular, a new effective action is obtained which enables us to
describe the array at arbitrary temperature. In the low temperature limit, our
theory yields the correct, dynamically screened Coulomb interaction of a normal
metal, whereas at high temperatures the standard description in terms of
quantum dissipation is recovered.Comment: 14 pages, 7 figure
First order superconducting transition near a ferromagnetic quantum critical point
We address the issue of how triplet superconductivity emerges in an
electronic system near a ferromagnetic quantum critical point (FQCP). Previous
studies found that the superconducting transition is of second order, and Tc is
strongly reduced near the FQCP due to pair-breaking effects from thermal spin
fluctuations. In contrast, we demonstrate that near the FQCP, the system avoids
pair-breaking effects by undergoing a first order transition at a much larger
Tc. A second order superconducting transition emerges only at some distance
from the FQCP.Comment: 4 pages, 2 figure