6,492 research outputs found
Ferromagnetism of Weakly-Interacting Electrons in Disordered Systems
It was realized two decades ago that the two-dimensional diffusive Fermi
liquid phase is unstable against arbitrarily weak electron-electron
interactions. Recently, using the nonlinear sigma model developed by
Finkelstein, several authors have shown that the instability leads to a
ferromagnetic state. In this paper, we consider diffusing electrons interacting
through a ferromagnetic exchange interaction. Using the Hartree-Fock
approximation to directly calculate the electron self energy, we find that the
total energy is minimized by a finite ferromagnetic moment for arbitrarily weak
interactions in two dimensions and for interaction strengths exceeding a
critical proportional to the conductivity in three dimensions. We discuss the
relation between our results and previous ones
Universal Description of Granular Metals at Low Temperatures: Granular Fermi Liquid
We present a unified description of the low temperature phase of granular
metals that reveals a striking generality of the low temperature behaviors. Our
model explains the universality of the low-temperature conductivity that
coincides exactly with that of the homogeneously disordered systems and enables
a straightforward derivation of low temperature characteristics of disordered
conductors.Comment: 4 pages, 1 figur
Are Bosonic Replicas Faulty?
Motivated by the ongoing discussion about a seeming asymmetry in the
performance of fermionic and bosonic replicas, we present an exact,
nonperturbative approach to zero-dimensional replica field theories belonging
to the broadly interpreted "beta=2" Dyson symmetry class. We then utilise the
formalism developed to demonstrate that the bosonic replicas do correctly
reproduce the microscopic spectral density in the QCD inspired chiral Gaussian
unitary ensemble. This disproves the myth that the bosonic replica field
theories are intrinsically faulty.Comment: 4.3 pages; final version to appear in PR
School Food Environments and Policies in U.S. Public Schools
Examines food environments in elementary, middle, and high schools based on seventeen factors, including foods and beverages offered, the availability of vending machines, and how they vary by grade level, location, and other school characteristics
Renormalization of hole-hole interaction at decreasing Drude conductivity
The diffusion contribution of the hole-hole interaction to the conductivity
is analyzed in gated GaAs/InGaAs/GaAs heterostructures. We show
that the change of the interaction correction to the conductivity with the
decreasing Drude conductivity results both from the compensation of the singlet
and triplet channels and from the arising prefactor in the
conventional expression for the interaction correction.Comment: 6 pages, 5 figure
The Costs of Obesity and Implications for Policymakers
Obesity, Direct Costs, Indirect Costs, Policy, Food Consumption/Nutrition/Food Safety, I10, I18,
Disordered electron liquid in double quantum well heterostructures: Renormalization group analysis and dephasing rate
We report a detailed study of the influence of the electron-electron
interaction on physical observables (conductance, etc.) of a disordered
electron liquid in double quantum well heterostructure. We find that even in
the case of common elastic scattering off electrons in both quantum wells, the
asymmetry in the electron-electron interaction across and within quantum wells
decouples them at low temperatures. Our results are in quantitative agreement
with recent transport experiments on the gated double quantum well
AlGaAs/GaAs/AlGaAs heterostructures.Comment: 15 pages; 5 figure
Critical behavior of density of states near Fermi energy in low-dimensional disordered metals
We study the effect of electron-electron interaction on the one-particle
density of states (\emph{DOS}) of low-dimensional
disordered metals near Fermi energy within the framework of the finite
temperature conventional impurity diagram technique. We consider only diffusive
limit and by a geometric re-summation of the most singular first order
self-energy corrections via the Dyson equation we obtain a non-divergent
solution for the \emph{DOS} at low energies, while for higher energies the
well-known Altshuler-Aronov corrections are recovered. At the Fermi level
, this indicates that interacting disordered
two- and quasi-one-dimensional systems are in insulating state at zero
temperature. The obtained results are in good agreement with recent tunneling
experiments on two-dimensional GaAs/AlGaAs heterostructures and
quasi-one-dimensional doped multiwall carbon nanotubes.Comment: 8 pages, 4 figure
Quantum percolation in granular metals
Theory of quantum corrections to conductivity of granular metal films is
developed for the realistic case of large randomly distributed tunnel
conductances. Quantum fluctuations of intergrain voltages (at energies E much
below bare charging energy scale E_C) suppress the mean conductance \bar{g}(E)
much stronger than its standard deviation \sigma(E). At sufficiently low
energies E_* any distribution becomes broad, with \sigma(E_*) ~ \bar{g}(E_*),
leading to strong local fluctuations of the tunneling density of states.
Percolative nature of metal-insulator transition is established by combination
of analytic and numerical analysis of the matrix renormalization group
equations.Comment: 6 pages, 5 figures, REVTeX
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