191 research outputs found
Order parameter and detection for crystallized dipolar bosons in lattices
We explore the ground-state properties of bosons with dipole-dipole
interactions in a one-dimensional optical lattice. Remarkably, a
crystallization process happens for strong dipolar interactions. Herein, we
provide a detailed characterization and a way to measure the resulting crystal
phase. Using the eigenvalues of the reduced one-body density matrix we define
an order parameter that yields a phase diagram in agreement with an analysis of
the density and two-body density. We demonstrate that the phase diagram can be
detected experimentally using the variance of single-shot measurements.Comment: 6 pages, 3 figures. Supplementary Information included. Software
available at http://ultracold.org
Condensate fragmentation as a sensitive measure of the quantum many-body behavior of bosons with long-range interactions
The occupation of more than one single-particle state and hence the emergence
of fragmentation is a many-body phenomenon universal to systems of spatially
confined interacting bosons. In the present study, we investigate the effect of
the range of the interparticle interactions on the fragmentation degree of one-
and two-dimensional systems. We solve the full many-body Schr\"odinger equation
of the system using the recursive implementation of the multiconfigurational
time-dependent Hartree for bosons method, R-MCTDHB. The dependence of the
degree of fragmentation on dimensionality, particle number, areal or line
density and interaction strength is assessed. It is found that for contact
interactions, the fragmentation is essentially density independent in two
dimensions. However, fragmentation increasingly depends on density the more
long-ranged the interactions become. The degree of fragmentation is increasing,
keeping the particle number fixed, when the density is decreasing as
expected in one spatial dimension. We demonstrate that this remains,
nontrivially, true also for long-range interactions in two spatial dimensions.
We, finally, find that within our fully self-consistent approach, the
fragmentation degree, to a good approximation, decreases universally as
when only is varied.Comment: 8 pages of RevTex4-1, 5 figure
Detecting One-Dimensional Dipolar Bosonic Crystal Orders via Full Distribution Functions
We explore the groundstates of a few dipolar bosons in optical lattices with
incommensurate filling. The competition of kinetic, potential, and interaction
energies leads to the emergence of a variety of crystal state orders with
characteristic one- and two-body densities. We probe the transitions between
these orders and construct the emergent state diagram as a function of the
dipolar interaction strength and the lattice depth. We show that the crystal
state orders can be observed using the full distribution functions of the
particle number extracted from simulated single-shot images.Comment: 6 pages, 3 Figures in main text. Supplementary Information included.
This version accepted for publication at Physical Review Letters. Software
for the computations available at http://www.ultracold.or
Superlattice switching from parametric instabilities in a driven-dissipative BEC in a cavity
We numerically obtain the full time-evolution of a parametrically-driven
dissipative Bose-Einstein condensate in an optical cavity and investigate the
implications of driving for the phase diagram. Beyond the normal and
superradiant phases, a third nonequilibrium phase emerges as a manybody
parametric resonance. This dynamical normal phase switches between two
symmetry-broken superradiant configurations. The switching implies a breakdown
of the system's mapping to the Dicke model. Unlike the other phases, the
dynamical normal phase shows features of nonintegrability and thermalization.Comment: 5 pages, 3 figure
Breaking the resilience of a two-dimensional Bose-Einstein condensate to fragmentation
A two-dimensional Bose-Einstein condensate (BEC) split by a radial potential
barrier is investigated. We determine on an accurate many-body level the
system's ground-state phase diagram as well as a time-dependent phase diagram
of the splitting process. Whereas the ground state is condensed for a wide
range of parameters, the time-dependent splitting process leads to substantial
fragmentation. We demonstrate for the first time the dynamical fragmentation of
a BEC despite its ground state being condensed. The results are analyzed by a
mean-field model and suggest that a large manifold of low-lying fragmented
excited states can significantly impact the dynamics of trapped two-dimensional
BECs.Comment: 5+eps pages, 4 figure
Phases, many-body entropy measures and coherence of interacting bosons in optical lattices
Already a few bosons with contact interparticle interactions in small optical
lattices feature a variety of quantum phases: superfluid, Mott-insulator and
fermionized Tonks gases can be probed in such systems. To detect these phases
-- pivotal for both experiment and theory -- as well as their many-body
properties we analyze several distinct measures for the one-body and many-body
Shannon information entropies. We exemplify the connection of these entropies
with spatial correlations in the many-body state by contrasting them to the
Glauber normalized correlation functions. To obtain the ground-state for
lattices with commensurate filling (i.e. an integer number of particles per
site) for the full range of repulsive interparticle interactions we utilize the
multiconfigurational time-dependent Hartree method for bosons (MCTDHB) in order
to solve the many-boson Schr\"odinger equation. We demonstrate that all
emergent phases -- the superfluid, the Mott insulator, and the fermionized gas
can be characterized equivalently by our many-body entropy measures and by
Glauber's normalized correlation functions. In contrast to our many-body
entropy measures, single-particle entropy cannot capture these transitions.Comment: 11 pages, 7 figures, software available at http://ultracold.or
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