950 research outputs found
Supersolid phase with cold polar molecules on a triangular lattice
We study a system of heteronuclear molecules on a triangular lattice and
analyze the potential of this system for the experimental realization of a
supersolid phase. The ground state phase diagram contains superfluid, solid and
supersolid phases. At finite temperatures and strong interactions there is an
additional emulsion region, in contrast to similar models with short-range
interactions. We derive the maximal critical temperature and the
corresponding entropy for supersolidity and find feasible
experimental conditions for its realization.Comment: 4 pages, 4 figure
Two-body bound and edge states in the extended SSH Bose-Hubbard model
We study the bosonic two-body problem in a Su-Schrieffer-Heeger dimerized
chain with on-site and nearest-neighbor interactions. We find two classes of
bound states. The first, similar to the one induced by on-site interactions,
has its center of mass on the strong link, whereas the second, existing only
thanks to nearest-neighbors interactions, is centered on the weak link. We
identify energy crossings between these states and analyse them using exact
diagonalization and perturbation theory. In the presence of open boundary
conditions, novel strongly-localized edge-bound states appear in the spectrum
as a consequence of the interplay between lattice geometry, on-site and
nearest-neighbor interactions. Contrary to the case of purely on-site
interactions, such EBS persist even in the strongly interacting regime.Comment: 12 pages, 8 figures; Submitted to EPJ Special Topics, Quantum Gases
and Quantum Coherenc
Nonlinear effects for Bose Einstein condensates in optical lattices
We present our experimental investigations on the subject of dynamical
nonlinearity-induced instabilities and of nonlinear Landau-Zener tunneling
between two energy bands in a Rubidium Bose-Einstein condensate in an
accelerated periodic potential. These two effects may be considered two
different regimes (for small and large acceleration) of the same physical
system and studied with the same experimental protocol. Nonlinearity introduces
an asymmetry in Landau-Zener tunneling; as a result, tunneling from the ground
state to the excited state is enhanced whereas in the opposite direction it is
suppressed. When the acceleration is lowered, the condensate exhibits an
unstable behaviour due to nonlinearity. We also carried out a full numerical
simulation of both regimes integrating the full Gross-Pitaevskii equation; for
the Landau-Zener effect we also used a simple two-level model. In both cases we
found good agreement with the experimental results.Comment: 9 pages, 7 figures. Submitted to Laser Physic
Velocity of sound in a Bose-Einstein condensate in the presence of an optical lattice and transverse confinement
We study the effect of the transverse degrees of freedom on the velocity of
sound in a Bose-Einstein condensate immersed in a one-dimensional optical
lattice and radially confined by a harmonic trap. We compare the results of
full three-dimensional calculations with those of an effective 1D model based
on the equation of state of the condensate. The perfect agreement between the
two approaches is demonstrated for several optical lattice depths and
throughout the full crossover from the 1D mean-field to the Thomas Fermi regime
in the radial direction.Comment: final versio
Particle-hole character of the Higgs and Goldstone modes in strongly-interacting lattice bosons
We study the low-energy excitations of the Bose-Hubbard model in the
strongly-interacting superfluid phase using a Gutzwiller approach and extract
the single-particle and single-hole excitation amplitudes for each mode. We
report emergent mode-dependent particle-hole symmetry on specific arc-shaped
lines in the phase diagram connecting the well-known Lorentz-invariant limits
of the Bose-Hubbard model. By tracking the in-phase particle-hole symmetric
oscillations of the order parameter, we provide an answer to the long-standing
question about the fate of the pure amplitude Higgs mode away from the
integer-density critical point. Furthermore, we point out that out-of-phase
oscillations are responsible for a full suppression of the condensate density
oscillations of the gapless Goldstone mode. Possible detection protocols are
also discussed.Comment: 6 pages, 3 figure
One-dimensional description of a Bose-Einstein condensate in a rotating closed-loop waveguide
We propose a general procedure for reducing the three-dimensional Schrodinger
equation for atoms moving along a strongly confining atomic waveguide to an
effective one-dimensional equation. This procedure is applied to the case of a
rotating closed-loop waveguide. The possibility of including mean-field atomic
interactions is presented. Application of the general theory to characterize a
new concept of atomic waveguide based on optical tweezers is finally discussed
Metastable states of a gas of dipolar bosons in a 2D optical lattice
We investigate the physics of dipolar bosons in a two dimensional optical
lattice. It is known that due to the long-range character of dipole-dipole
interaction, the ground state phase diagram of a gas of dipolar bosons in an
optical lattice presents novel quantum phases, like checkerboard and supersolid
phases. In this paper, we consider the properties of the system beyond its
ground state, finding that it is characterised by a multitude of almost
degenerate metastable states, often competing with the ground state. This makes
dipolar bosons in a lattice similar to a disordered system and opens
possibilities of using them for quantum memories.Comment: small improvements in the text, Fig.4 replaced, added and updated
references. 4 pages, 4 figures, to appear in Phys. Rev. Let
Scalable squeezed light source for continuous variable quantum sampling
We propose a novel squeezed light source capable of meeting the stringent
requirements of continuous variable quantum sampling. Using the effective
interaction induced by a strong driving beam in the presence of the
response in an integrated microresonator, our device is compatible
with established nanophotonic fabrication platforms. With typical realistic
parameters, squeezed states with a mean photon number of 10 or higher can be
generated in a single consistent temporal mode at repetition rates in excess of
100MHz. Over 15dB of squeezing is achievable in existing ultra-low loss
platforms
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