3,833 research outputs found
The sonic analogue of black hole radiation
A microscopic description of Hawking radiation in sonic black holes has been
recently presented (Giovanazzi S 2005 Phys. Rev. Lett. 94 061302). This exactly
solvable model is formulated in terms of one-dimensional scattering of a Fermi
gas. In this paper, the model is extended to account possible finite size
effects of a realistic geometry. The flow of particles is maintained by a
piston (i.e. an impenetrable barrier) moving slowly towards the sonic horizon.
Using existing technologies the Hawking temperature can be of order of a few
microkelvin in a realistic experiment.Comment: 14 pages, 7 figures, submitted to Journal of Physics B: Atomic,
Molecular & Optical Physic
Stability of the shell structure in 2D quantum dots
We study the effects of external impurities on the shell structure in
semiconductor quantum dots by using a fast response-function method for solving
the Kohn-Sham equations. We perform statistics of the addition energies up to
20 interacting electrons. The results show that the shell structure is
generally preserved even if effects of high disorder are clear. The Coulomb
interaction and the variation in ground-state spins have a strong effect on the
addition-energy distributions, which in the noninteracting single-electron
picture correspond to level statistics showing mixtures of Poisson and Wigner
forms.Comment: 7 pages, 8 figures, submitted to Phys. Rev.
Nonlinear screening of charge impurities in graphene
It is shown that a ``vacuum polarization'' induced by Coulomb potential in
graphene leads to a strong suppression of electric charges even for undoped
case (no charge carriers). A standard linear response theory is therefore not
applicable to describe the screening of charge impurities in graphene. In
particular, it overestimates essentially the contributions of charge impurities
into the resistivity of graphene.Comment: 3 pages, 1 figure; final version as published in the journa
Dynamic spin response of a strongly interacting Fermi gas
We present an experimental investigation of the dynamic spin response of a
strongly interacting Fermi gas using Bragg spectroscopy. By varying the
detuning of the Bragg lasers, we show that it is possible to measure the
response in the spin and density channels separately. At low Bragg energies,
the spin response is suppressed due to pairing, whereas the density response is
enhanced. These experiments provide the first independent measurements of the
spin-parallel and spin-antiparallel dynamic and static structure factors and
open the way to a complete study of the structure factors at any momentum. At
high momentum the spin-antiparallel dynamic structure factor displays a
universal high frequency tail, proportional to , where is the probe energy.Comment: Replaced with final versio
Dispersive effects in neutron matter superfluidity
The explicit energy dependence of the single particle self-energy (dispersive
effects), due to short range correlations, is included in the treatment of
neutron matter superfluidity. The method can be applied in general to strong
interacting fermion systems, and it is expected to be valid whenever the
pairing gap is substantially smaller than the Fermi kinetic energy. The results
for neutron matter show that dispersive effects are strong in the density
region near the gap closure.Comment: 9 pages, 4 ps figure
Quasiparticle Self-Consistent GW Theory
In past decades the scientific community has been looking for a reliable
first-principles method to predict the electronic structure of solids with high
accuracy. Here we present an approach which we call the quasiparticle
self-consistent GW approximation (QpscGW). It is based on a kind of
self-consistent perturbation theory, where the self-consistency is constructed
to minimize the perturbation. We apply it to selections from different classes
of materials, including alkali metals, semiconductors, wide band gap
insulators, transition metals, transition metal oxides, magnetic insulators,
and rare earth compounds. Apart some mild exceptions, the properties are very
well described, particularly in weakly correlated cases. Self-consistency
dramatically improves agreement with experiment, and is sometimes essential.
Discrepancies with experiment are systematic, and can be explained in terms of
approximations made.Comment: 12 pages, 3 figure
Mesoscopic Transport: The Electron-Gas Sum Rules in a Driven Quantum Point Contact
The nature of the electron gas is characterized, above all, by its
multi-particle correlations. The conserving sum rules for the electron gas have
been thoroughly studied for many years, and their centrality to the physics of
metallic conduction is widely understood (at least in the many-body community).
We review the role of the conserving sum rules in mesoscopic transport, as
normative criteria for assessing the conserving status of mesoscopic models. In
themselves, the sum rules are specific enough to rule out any such theory if it
fails to respect the conservation laws. Of greater interest is the capacity of
the compressibility sum rule, in particular, to reveal unexpected fluctuation
effects in nonuniform mesoscopic structures.Comment: TeX, 11pp, no fi
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