1,696 research outputs found
Random-Manifold to Random-Periodic Depinning of an Elastic Interface
We study numerically the depinning transition of driven elastic interfaces in
a random-periodic medium with localized periodic-correlation peaks in the
direction of motion. The analysis of the moving interface geometry reveals the
existence of several characteristic lengths separating different length-scale
regimes of roughness. We determine the scaling behavior of these lengths as a
function of the velocity, temperature, driving force, and transverse
periodicity. A dynamical roughness diagram is thus obtained which contains, at
small length scales, the critical and fast-flow regimes typical of the
random-manifold (or domain wall) depinning, and at large length-scales, the
critical and fast-flow regimes typical of the random-periodic (or
charge-density wave) depinning. From the study of the equilibrium geometry we
are also able to infer the roughness diagram in the creep regime, extending the
depinning roughness diagram below threshold. Our results are relevant for
understanding the geometry at depinning of arrays of elastically coupled thin
manifolds in a disordered medium such as driven particle chains or vortex-line
planar arrays. They also allow to properly control the effect of transverse
periodic boundary conditions in large-scale simulations of driven disordered
interfaces.Comment: 19 pages, 10 figure
Thermal rounding exponent of the depinning transition of an elastic string in a random medium
We study numerically thermal effects at the depinning transition of an
elastic string driven in a two-dimensional uncorrelated disorder potential. The
velocity of the string exactly at the sample critical force is shown to behave
as , with the thermal rounding exponent. We show that the
computed value of the thermal rounding exponent, , is robust and
accounts for the different scaling properties of several observables both in
the steady-state and in the transient relaxation to the steady-state. In
particular, we show the compatibility of the thermal rounding exponent with the
scaling properties of the steady-state structure factor, the universal
short-time dynamics of the transient velocity at the sample critical force, and
the velocity scaling function describing the joint dependence of the
steady-state velocity on the external drive and temperature
Mode coupling induced dissipative and thermal effects at long times after a quantum quench
An interaction quench in a Luttinger liquid can drive it into an athermal
steady state. We analyze the effects on such an out of equilibrium state of a
mode coupling term due to a periodic potential. Employing a perturbative
renormalization group approach we show that even when the periodic potential is
an irrelevant perturbation in equilibrium, it has important consequences on the
athermal steady state as it generates a temperature as well as a dissipation
and hence a finite life-time for the bosonic modes.Comment: 4+ pages and 2 figure
Deconfinement and cold atoms in optical lattices
Despite the fact that by now one dimensional and three dimensional systems of
interacting particles are reasonably well understood, very little is known on
how to go from the one dimensional physics to the three dimensional one. This
is in particular true in a quasi-one dimensional geometry where the hopping of
particles between one dimensional chains or tubes can lead to a dimensional
crossover between a Luttinger liquid and more conventional high dimensional
states. Such a situation is relevant to many physical systems. Recently cold
atoms in optical traps have provided a unique and controllable system in which
to investigate this physics. We thus analyze a system made of coupled one
dimensional tubes of interacting fermions. We explore the observable
consequences, such as the phase diagram for isolated tubes, and the possibility
to realize unusual superfluid phases in coupled tubes systems.Comment: Proceedings of the conference on "Quantum Many Body Theories 13", to
be published by World Scientifi
Hall effect in quasi one-dimensional organic conductors
We study the Hall effect in a system of weakly coupled Luttinger Liquid
chains, using a Memory function approach to compute the Hall constant in the
presence of umklapp scattering along the chains. In this approximation, the
Hall constant decomposes into two terms: a high-frequency term and a Memory
function term. For the case of zero umklapp scattering, where the Memory
function vanishes, the Hall constant is simply the band value, in agreement
with former results in a similar model with no dissipation along the chains.
With umklapp scattering along the chains, we find a power-law temperature
dependance of the Hall constant. We discuss the applications to quasi 1D
organic conductors at high temperatures.Comment: Proceedings of the ISCOM conference "Sixth International Symposium on
Crystalline Organic Metals, Superconductors, and Ferromagnets", Key West,
Florida, USA (Sept. 2005), to be plublished in the Journal of Low Temperature
Physic
Thermal rounding of the depinning transition
We study thermal effects at the depinning transition by numerical simulations
of driven one-dimensional elastic interfaces in a disordered medium. We find
that the velocity of the interface, evaluated at the critical depinning force,
can be correctly described with the power law , where is
the thermal exponent. Using the sample-dependent value of the critical force,
we precisely evaluate the value of directly from the temperature
dependence of the velocity, obtaining the value . By
measuring the structure factor of the interface we show that both the
thermally-rounded and the T=0 depinning, display the same large-scale geometry,
described by an identical divergence of a characteristic length with the
velocity , where and are respectively
the T=0 correlation and depinning exponents. We discuss the comparison of our
results with previous estimates of the thermal exponent and the direct
consequences for recent experiments on magnetic domain wall motion in
ferromagnetic thin films.Comment: 6 pages, 3 figure
Oscillating Casimir force between impurities in one-dimensional Fermi liquids
We study the interaction of two localized impurities in a repulsive
one-dimensional Fermi liquid via bosonization. In a previous paper [Phys. Rev.
A 72, 023616 (2005)], it was shown that at distances much larger than the
interparticle spacing the impurities interact through a Casimir-type force
mediated by the zero sound phonons of the underlying quantum liquid. Here we
extend these results and show that the strength and sign of this Casimir
interaction depend sensitively on the impurities separation. These oscillations
in the Casimir interaction have the same period as Friedel oscillations. Their
maxima correspond to tunneling resonances tuned by the impurities separation.Comment: This paper is a continuation of Phys. Rev. A 72, 023616 (2005). v2:
two appendix adde
Specific heat of the quantum Bragg Glass
We study the thermodynamics of the vibrational modes of a lattice pinned by
impurity disorder in the absence of topological defects (Bragg glass phase).
Using a replica variational method we compute the specific heat in the
quantum regime and find at low temperatures in dimension
three and two. The prefactor is controlled by the pinning length. The non
trivial cancellation of the linear term in arises from the so-called
marginality condition and has important consequences for other mean field
models.Comment: 5 pages, RevTex, strongly revised versio
Time-evolution and dynamical phase transitions at a critical time in a system of one dimensional bosons after a quantum quench
A renormalization group approach is used to show that a one dimensional
system of bosons subject to a lattice quench exhibits a finite-time dynamical
phase transition where an order parameter within a light-cone increases as a
non-analytic function of time after a critical time. Such a transition is also
found for a simultaneous lattice and interaction quench where the effective
scaling dimension of the lattice becomes time-dependent, crucially affecting
the time-evolution of the system. Explicit results are presented for the
time-evolution of the boson interaction parameter and the order parameter for
the dynamical transition as well as for more general quenches.Comment: final published versio
Quantum Simulation of the Hubbard Model: The Attractive Route
We study the conditions under which, using a canonical transformation, the
phases sought after for the repulsive Hubbard model, namely a Mott insulator in
the paramagnetic and anti-ferromagnetic phases, and a putative d-wave
superfluid can be deduced from observations in an optical lattice loaded with a
spin-imbalanced ultra-cold Fermi gas with attractive interactions, thus
realizing the attractive Hubbard model. We show that the Mott insulator and
antiferromagnetic phase of the repulsive Hubbard model are in fact more easy to
observe as a paired, and superfluid phase respectively, in the attractive
Hubbard model. The putative d-wave superfluid phase of the repulsive Hubbard
model doped away from half-filling is related to a d-wave antiferromagnetic
phase for the attractive Hubbard model. We discuss the advantages of this
approach to 'quantum simulate' the Hubbard model in an optical lattice over the
approach that attempts to directly simulate the doped Hubbard model in the
repulsive regime. We also point out a number of technical difficulties of the
proposed approach and, in some cases, suggest possible solutions.Comment: 11 pages, 5 figs. New version as accepted in PRA. We have clarified
the models we are discussing in various places, and expanded on the critical
number estimate to include both K40 and Li6 in section V. Also added
reference
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