67 research outputs found
Momentum relaxation of a mobile impurity in a one-dimensional quantum gas
We investigate the time evolution of the momentum of an impurity atom
injected into a degenerate Tonks-Girardeau gas. We establish that given an
initial momentum the impurity relaxes to a steady state with a
non-vanishing momentum The nature of the steady state is found to
depend drastically on whether the masses of the impurity and the host are equal
or not. This is due to multiple coherent scattering processes leading to a
resonant interaction between the impurity and the host in the case of equal
masses. The dependence of on remains non-trivial even in the
limit of vanishing interaction between the impurity and host particles. In this
limit is found explicitly
Thermodynamics of the 3D Hubbard model on approach to the Neel transition
We study the thermodynamic properties of the 3D Hubbard model for
temperatures down to the Neel temperature using cluster dynamical mean-field
theory. In particular we calculate the energy, entropy, density, double
occupancy and nearest-neighbor spin correlations as a function of chemical
potential, temperature and repulsion strength. To make contact with cold-gas
experiments, we also compute properties of the system subject to an external
trap in the local density approximation. We find that an entropy per particle
at is sufficient to achieve a Neel state in the
center of the trap, substantially higher than the entropy required in a
homogeneous system. Precursors to antiferromagnetism can clearly be observed in
nearest-neighbor spin correlators.Comment: 4 pages, 6 figure
Diagrammatic Quantum Monte Carlo solution of the two-dimensional Cooperon-Fermion model
We investigate the two-dimensional cooperon-fermion model in the correlated
regime with a new continuous-time diagrammatic determinant quantum Monte Carlo
(DDQMC) algorithm. We estimate the transition temperature , examine the
effectively reduced band gap and cooperon mass, and find that delocalization of
the cooperons enhances the diamagnetism. When applied to diamagnetism of the
pseudogap phase in high- cuprates, we obtain results in a qualitative
agreement with recent torque magnetization measurements.Comment: 8 pages, 11 figure
Thermodynamics of localized magnetic moments in a Dirac conductor
We show that the magnetic susceptibility of a dilute ensemble of magnetic
impurities in a conductor with a relativistic electronic spectrum is
non-analytic in the inverse tempertature at . We derive a general
theory of this effect and construct the high-temperature expansion for the
disorder averaged susceptibility to any order, convergent at all tempertaures
down to a possible ordering transition. When applied to Ising impurities on a
surface of a topological insulator, the proposed general theory agrees with
Monte Carlo simulations, and it allows us to find the critical temperature of
the ferromagnetic phase transition.Comment: 5 pages, 1 figure, 2 tables, RevTe
High Precision Measurement of the Thermal Exponent for the Three-Dimensional XY Universality Class
Simulations results are reported for critical point of the two-component
field theory. The correlation length exponent is measured to high
precision with the result . This value is in agreement with
recent simulation results [Campostrini \textit{et al}., Phys. Rev. B
\textbf{63}, 214503 (2001)], and marginally agrees with the most recent
space-based measurements of the superfluid transition in He [Lipa
\textit{et al}., Phys. Rev. B \textbf{68}, 174518 (2003)].Comment: a reference adde
Three fermions in a box at the unitary limit: universality in a lattice model
We consider three fermions with two spin components interacting on a lattice
model with an infinite scattering length. Low lying eigenenergies in a cubic
box with periodic boundary conditions, and for a zero total momentum, are
calculated numerically for decreasing values of the lattice period. The results
are compared to the predictions of the zero range Bethe-Peierls model in
continuous space, where the interaction is replaced by contact conditions. The
numerical computation, combined with analytical arguments, shows the absence of
negative energy solution, and a rapid convergence of the lattice model towards
the Bethe-Peierls model for a vanishing lattice period. This establishes for
this system the universality of the zero interaction range limit.Comment: 6 page
Anisotropic Ginzburg-Landau and Lawrence-Doniach Models for Layered Ultracold Fermi Gases
We study the anisotropic Ginzburg-Landau and Lawrence-Doniach models
describing a layered superfluid ultracold Fermi gas in optical lattices. We
derive the coefficients of the anisotropic Ginzburg-Landau and the mass tensor
as a function of anisotropy, filling and interaction, showing that near the
unitary limit the effective anisotropy of the masses is significantly reduced.
The anisotropy parameter is shown to vary in realistic setups in a wide range
of values. We also derive the Lawrence-Doniach model - often used to describe
the 2D-3D dimensional crossover in layered superconductors - for a layered
ultracold Fermi gas, obtaining a relation between the interlayer Josephson
couplings and the Ginzburg-Landau masses. Comparing to the Ginzburg-Landau
description, we find that the region of validity of the Lawrence-Doniach model
is near the unitary limit.Comment: 15 pages, 4 figure
Annealing Effect for Supersolid Fraction in He
We report on experimental confirmation of the non-classical rotational
inertia (NCRI) in solid helium samples originally reported by Kim and Chan. The
onset of NCRI was observed at temperatures below ~400 mK. The ac velocity for
initiation of the NCRI suppression is estimated to be ~10 m/sec. After an
additional annealing of the sample at K for 12 hours, ~ 10% relative
increase of NCRI fraction was observed. Then after repeated annealing with the
same conditions, the NCRI fraction was saturated. It differs from Reppy's
observation on a low pressure solid sample.Comment: to be published in J. of Low Temp. Phys. (QFS2006 proceedings
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