25 research outputs found
Analysis and resolution of the ground-state degeneracy of the two-component Bose-Hubbard model
We study the degeneracy of the ground-state energy of the two-component
Bose-Hubbard model and of the perturbative correction . We show that the
degeneracy properties of and are closely related to the connectivity
properties of the lattice. We determine general conditions under which is
nondegenerate. This analysis is then extended to investigate the degeneracy of
. In this case, in addition to the lattice structure, the degeneracy also
depends on the number of particles present in the system. After identifying the
cases in which is degenerate and observing that the standard (degenerate)
perturbation theory is not applicable, we develop a method to determine the
zeroth-order correction to the ground state by exploiting the symmetry
properties of the lattice. This method is used to implement the perturbative
approach to the two-component Bose-Hubbard model in the case of degenerate
and is expected to be a valid tool to perturbatively study the asymmetric
character of the Mott-insulator to superfluid transition between the particle
and hole side
Inter-species entanglement of Bose-Bose mixtures trapped in optical lattices
In the present work we discuss inter-species entanglement in Bose-Bose
mixtures trapped in optical lattices. This work is motivated by the observation
that, in the presence of a second component, the Mott-insulator lobe shifts
{\em{differently}} on the hole- and particle-side with respect to the Mott lobe
of the single species system (Phys. Rev. A 82, 021601, Laser Phys. 21, 1443).
We use perturbation theory, formulated in a Hilbert space decomposed by means
of lattice symmetries, in order to show that the nonuniform shift of the Mott
lobe is a consequence of an inter-species entanglement which differs in the
lowest excited states to remove and add a particle. Our results indicate that
inter-species entanglement in mixtures can provide a new perspective in
understanding quantum phase transitions. To validate our approach, we compare
our results from perturbation theory with quantum Monte Carlo simulations
A topological signature of multipartite entanglement
In this manuscript, we present a proposal to relate topological structure of
worldline configurations to multipartite entanglement. Configurations result
from the path-integral formulation of the density matrix in the limit of zero
temperature. We consider hard-core bosons for which configurations, i.e.
collections of particle paths, can be seen as geometric braids with a certain
topological structure. We propose that properties of worldline configurations
may realize a comprehensive deciphering of multipartite entanglement. By means
of Monte Carlo calculations, we study checkerboard, stripe, valence-bond
solids, topologically ordered spin liquid, and superfluid phase.
We find that each ground-state is characterized by a certain `topological
spectrum' which can be used to differentiate among different ground-states.Comment: 6 pages, 3 figures and supplemental material. Version 2 focuses on
the discussion of topological signatures of multipartite entanglement in the
ground-state expansion, with added results. The study of phase transitions
and permutation cycles in version 1 has been moved to a new manuscript:
arXiv:1912.00080. Version 3 corrected some typos and reference
Quasi-molecular bosonic complexes -- a pathway to atomic analog of SQUID with controlled sensitivity
Recent experimental advances in realizing degenerate quantum dipolar gases in
optical lattices and the flexibility of experimental setups in attaining
various geometries offer the opportunity to explore exotic quantum many-body
phases stabilized by anisotropic, long-range dipolar interaction. Moreover, the
unprecedented control over the various physical properties of these systems,
ranging from the quantum statistics of the particles, to the inter-particle
interactions, allow one to engineer novel devices. In this paper, we consider
dipolar bosons trapped in a stack of one-dimensional optical lattice layers,
previously studied in [1]. Building on our prior results, we provide a
description of the quantum phases stabilized in this system which include
composite superfluids, solids, and supercounterfluids, most of which are found
to be threshold- less with respect to the dipolar interaction strength. We also
demonstrate the effect of enhanced sensitivity to rotations of a SQUID-type
device made of two composite superfluids trapped in a ring-shaped optical
lattice layer with weak links.Comment: Special Issue Articl
Monte Carlo study of two-dimensional Bose-Hubbard model
One of the most promising applications of ultracold gases in optical lattices
is the possibility to use them as quantum emulators of more complex condensed
matter systems. We provide benchmark calculations, based on exact quantum Monte
Carlo simulations, for the emulator to be tested against. We report results for
the ground state phase diagram of the two-dimensional Bose-Hubbard model at
unity filling factor. We precisely trace out the critical behavior of the
system and resolve the region of small insulating gaps, \Delta << J. The
critical point is found to be (J/U)_c=0.05974(3), in perfect agreement with the
high-order strong-coupling expansion method of Ref. 1. In addition, we present
data for the effective mass of particle and hole excitations inside the
insulating phase and obtain the critical temperature for the superfluid-normal
transition at unity filling factor.Comment: 4 pages 5 figures. Some changes in the text have been mad
Ising antiferromagnet with ultracold bosonic mixtures confined in a harmonic trap
We present accurate results based on Quantum Monte Carlo simulations of
two-component bosonic systems on a square lattice and in the presence of an
external harmonic confinement. Starting from hopping parameters and interaction
strengths which stabilize the Ising antiferromagnetic phase in the homogeneous
case and at half integer filling factor, we study how the presence of the
harmonic confinement challenge the realization of such phase. We consider
realistic trapping frequencies and number of particles, and establish under
which conditions, i.e. total number of particles and population imbalance, the
antiferromagnetic phase can be observed in the trap.Comment: 4 pages, 2 figures, accepted for publication on PRA as a Rapid
Communication. The present version contains lighter low resolution images.
For High resolution version please refer to Journa
Quantum phases of lattice dipolar bosons coupled to a high-finesse cavity
Two types of long-range interactions, dipolar interaction and cavity-mediated interaction, lead to exotic quantum phases. Both interactions were realized and observed in optical lattice setups. Here, we study quantum phases of dipolar bosons trapped in optical lattices and coupled to a high-finesse cavity where both dipolar interaction and cavity-mediated interaction coexist. We perform quantum Monte Carlo simulations and find that the checkerboard solid is enhanced and the checkerboard supersolid phase can exist in a wide range of densities (e.g., 0.27≲n≲0.73). Our unbiased numerical results suggest that both solid and supersolid phases can be achieved experimentally with magnetic atoms coupled to a cavity. © 2023 American Physical Society
Permutation cycles of hardcore Bose-Hubbard models on square and Kagome lattices
In this paper, we study the statistics of permutation cycles of ground-state
hardcore lattice bosons described by various two-dimensional Bose-Hubbard-type
models on both square and Kagome lattices. We find that it is possible to
differentiate quantum phases by the statistics of permutations cycles. Indeed,
features in the permutation cycles statistics can be used to uniquely identify
certain insulating phases, and are consistent with local resonances of
occupation numbers in the ground-state expansion of the phase. We also confirm
that suitable quantities derived from the probability distribution of the
length of permutation cycles can be used to detect superfluid to insulator
phase transitions.Comment: 7 pages, 9 figures. The study of phase transitions and permutation
cycles originally part of manuscript arXiv:1905.07454v1 (version 1) has been
moved to this manuscript while the discussion of topological signatures of
multipartite entanglement in the ground-state expansion has been further
developed in version 2 of manuscript arXiv:1905.07454v
Quantum phases of lattice dipolar bosons coupled to a high-finesse cavity
Two types of long range interactions, dipolar interaction and cavity-mediated
interaction lead to exotic quantum phases. Both interactions have been realized
and observed in optical lattice setups. Here, we study quantum phases of
dipolar bosons trapped in optical lattices and coupled to a high-finesse cavity
where both dipolar interaction and cavity-mediated interaction coexist. We
perform quantum Monte Carlo simulations, and find that the checkerboard solid
is enhanced and the checkerboard supersolid phase can exist in a wide range of
densities (e.g. ). Our unbiased numerical results
suggest that both solid and supersolid phases can be achieved experimentally
with magnetic atoms coupled to a cavity.Comment: 8 pages, 7 figure