251 research outputs found
Supercurrent survival under Rosen-Zener quench of hard core bosons
We study the survival of super-currents in a system of impenetrable bosons
subject to a quantum quench from its critical superfluid phase to an insulating
phase. We show that the evolution of the current when the quench follows a
Rosen-Zener profile is exactly solvable. This allows us to analyze a quench of
arbitrary rate, from a sudden destruction of the superfluid to a slow opening
of a gap. The decay and oscillations of the current are analytically derived,
and studied numerically along with the momentum distribution after the quench.
In the case of small supercurrent boosts , we find that the current
surviving at long times is proportional to
A thick shell Casimir effect
We consider the Casimir energy of a thick dielectric-diamagnetic shell under
a uniform velocity light condition, as a function of the radii and the
permeabilities. We show that there is a range of parameters in which the stress
on the outer shell is inward, and a range where the stress on the outer shell
is outward. We examine the possibility of obtaining an energetically stable
configuration of a thick shell made of a material with a fixed volume
Fermi-Edge Resonance and Tunneling in Nonequilibrium Electron Gas
Fermi-edge singularity changes in a dramatic way in a nonequilibrium system,
acquiring features which reflect the structure of energy distribution. In
particular, it splits into several components if the energy distribution
exhibits multiple steps. While conventional approaches, such as bosonization,
fail to describe the nonequilibrium problem, an exact solution for a generic
energy distribution can be obtained with the help of the method of functional
determinants. In the case of a split Fermi distribution, while the `open loop'
contribution to Green's function has power law singularities, the tunneling
density of states profile exhibits broadened peaks centered at Fermi
sub-levels.Comment: 5 pages, 1 figur
Dynamics of coherences in the interacting double-dot Aharonov-Bohm interferometer: Exact numerical simulations
We study the real time dynamics of electron coherence in a double quantum dot
two-terminal Aharonov-Bohm geometry, taking into account repulsion effects
between the dots' electrons. The system is simulated by extending a numerically
exact path integral method, suitable for treating transport and dissipation in
biased impurity models [Phys. Rev. B 82, 205323 (2010)]. Numerical simulations
at finite interaction strength are supported by master equation calculations in
two other limits: assuming non-interacting electrons, and working in the
Coulomb blockade regime. Focusing on the intrinsic coherence dynamics between
the double-dot states, we find that its temporal characteristics are preserved
under weak-to-intermediate inter-dot Coulomb interaction. In contrast, in the
Coulomb blockade limit, a master equation calculation predicts coherence
dynamics and a steady-state value which notably deviate from the finite
interaction case
Photon Green's function and the Casimir energy in a medium
A new expansion is established for the Green's function of the
electromagnetic field in a medium with arbitrary and . The
obtained Born series are shown to consist of two types of interactions - the
usual terms (denoted ) that appear in the Lifshitz theory combined with
a new kind of terms (which we denote by ) associated with the changes
in the permeability of the medium. Within this framework the case of uniform
velocity of light () is studied. We obtain expressions
for the Casimir energy density and the first non-vanishing contribution is
manipulated to a simplified form. For (arbitrary) spherically symmetric
we obtain a simple expression for the electromagnetic energy density, and as an
example we obtain from it the Casimir energy of a dielectric-diamagnetic ball.
It seems that the technique presented can be applied to a variety of problems
directly, without expanding the eigenmodes of the problem and using boundary
condition considerations
Casimir energy of a dilute dielectric ball with uniform velocity of light at finite temperature
The Casimir energy, free energy and Casimir force are evaluated, at arbitrary
finite temperature, for a dilute dielectric ball with uniform velocity of light
inside the ball and in the surrounding medium. In particular, we investigate
the classical limit at high temperature. The Casimir force found is repulsive,
as in previous calculations.Comment: 15 pages, 1 figur
Microscopic theory of resonant soft x-ray scattering in systems with charge order
We present a microscopic theory of resonant soft x-ray scattering (RSXS) that
accounts for the delocalized character of valence electrons. Unlike past
approaches defined in terms of form factors for atoms or clusters, we develop a
functional determinant method that allows us to treat realistic band
structures. This method builds upon earlier theoretical work in mesoscopic
physics and accounts for both excitonic effects as well as the orthogonality
catastrophe arising from interaction between the core hole and the valence band
electrons. Comparing to RSXS measurements from stripe-ordered LBCO, we show
that the two-peak structure observed near the O K edge can be understood as
arising from dynamic nesting within the canonical cuprate band structure. Our
results provide evidence for reasonably well-defined, high-energy
quasiparticlesComment: 7 pages, 2 figure
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