1,141 research outputs found
Comment on "Density of States and Critical Behavior of the Coulomb Glass"
In a recent numerical investigation of the Coulomb glass, Surer et al. [Phys.
Rev. Lett. 102, 067205 (2009)] concluded that their simulation results are
consistent with the Efros Shklovskii prediction for the density of states in
the three-dimensional case. Here, we show that this statement has no relevance
concerning the problem of the asymptotic behavior in the Coulomb gap since it
is based on unjustified assumptions. Moreover, for the random-displacement
Coulomb glass model, we demonstrate that a part of the density of states data
by Surer et al. erroneously exhibit a broad gap. This is related to the
staggered occupation being instable contrary to their findings.Comment: Submitted to Physical Review Letters, 1 page, 1 figur
Non-ergodic effects in the Coulomb glass: specific heat
We present a numerical method for the investigation of non-ergodic effects in
the Coulomb glass. For that, an almost complete set of low-energy many-particle
states is obtained by a new algorithm. The dynamics of the sample is mapped to
the graph formed by the relevant transitions between these states, that means
by transitions with rates larger than the inverse of the duration of the
measurement. The formation of isolated clusters in the graph indicates
non-ergodicity. We analyze the connectivity of this graph in dependence on
temperature, duration of measurement, degree of disorder, and dimensionality,
studying how non-ergodicity is reflected in the specific heat.Comment: Submited Phys. Rev.
Dielectric susceptibility of the Coulomb-glass
We derive a microscopic expression for the dielectric susceptibility
of a Coulomb glass, which corresponds to the definition used in classical
electrodynamics, the derivative of the polarization with respect to the
electric field. The fluctuation-dissipation theorem tells us that is a
function of the thermal fluctuations of the dipole moment of the system. We
calculate numerically for three-dimensional Coulomb glasses as a
function of temperature and frequency
Source of entangled atom pairs on demand, using the Rydberg blockade
Two ultracold atom clouds, each separately in a dipole-blockade regime,
realize a source of entangled atom pairs that can be ejected on demand.
Entanglement generation and ejection is due to resonant dipole-dipole
interactions, while van-der-Waals interactions are predominantly responsible
for the blockade that ensures the ejection of a single atom per cloud. A source
of entangled atoms using these effects can operate with a 10 kHz repetition
rate producing ejected atoms with velocities of about 0.5 m/s.Comment: 7 pages, 4 figure
Response to the Comment on "Excitons in Molecular Aggregates with L\'evy Disorder: Anomalous Localization and Exchange Broadening of Optical Spectra"
In previous work, we have predicted novel effects, such as exchange
broadening, anomalous scaling of the localization length and a blue shift of
the absorption spectrum with increasing disorder strength, for static disorder
models described by stable distributions with stability index {\alpha}<1. The
main points of the Comment are that the outliers introduced by heavy tails in
the disorder distribution (i) do not lead to deviations from the conventional
scaling law for the half width at half maximum (HWHM) of the absorption
spectrum and (ii) do not lead to non-universality of the distribution of
localization lengths. We show below that the findings reported by us in the
Letter are correct and that the wrong conclusions of the Comment arise from
focusing on small {\sigma} values.Comment: Based on our response submitted to Physical Review Letters on January
20, 2012. We now also take into account the modifications made to the Comment
upon resubmission of the Comment. The Reply has been accepted in Physical
Review Letter
Dipole-dipole induced global motion of Rydberg-dressed atom clouds
We consider two clouds of ground state alkali atoms in two distinct hyperfine
ground states. Each level is far off-resonantly coupled to a Rydberg state,
which leads to dressed ground states with a weak admixture of the Rydberg state
properties. Due to this admixture, for a proper choice of the Rydberg states,
the atoms experience resonant dipole-dipole interactions that induce mechanical
forces acting on all atoms within both clouds. This behavior is in contrast to
the dynamics predicted for bare dipole-dipole interactions between Rydberg
superatoms, where only a single atom per cloud is subject to dipole-dipole
induced motion [Phys. Rev. A {\bf 88} 012716 (2013)].Comment: 15 pages, 2 figure
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