78 research outputs found
Homogeneous and inhomogeneous magnetic phases of constrained dipolar bosons
We study the emergence of several magnetic phases in dipolar bosonic gases
subject to three-body loss mechanism employing numerical simulations based on
the density matrix renormalization group(DMRG) algorithm. After mapping the
original Hamiltonian in spin language, we find a strong parallelism between the
bosonic theory and the spin-1 Heisenberg model with single ion anisotropy and
long-range interactions. A rich phase diagram, including ferromagnetic,
antiferromagnetic and non-local ordered phases, emerges in the half-filled
one-dimensional case, and is preserved even in presence of a trapping
potential.Comment: v2: 9 pages, 15 figures, extended version, new numerical calculations
on the BKT transition, accepted for pubblication in PR
Majorana Quasi-Particles Protected by Angular Momentum Conservation
We show how angular momentum conservation can stabilise a symmetry-protected
quasi-topological phase of matter supporting Majorana quasi-particles as edge
modes in one-dimensional cold atom gases. We investigate a number-conserving
four-species Hubbard model in the presence of spin-orbit coupling. The latter
reduces the global spin symmetry to an angular momentum parity symmetry, which
provides an extremely robust protection mechanism that does not rely on any
coupling to additional reservoirs. The emergence of Majorana edge modes is
elucidated using field theory techniques, and corroborated by
density-matrix-renormalization-group simulations. Our results pave the way
toward the observation of Majorana edge modes with alkaline-earth-like fermions
in optical lattices, where all basic ingredients for our recipe - spin-orbit
coupling and strong inter-orbital interactions - have been experimentally
realized over the last two years.Comment: 12 pages (6 + 6 supplementary material
Phase separation and pairing regimes in the one-dimensional asymmetric Hubbard model
We address some open questions regarding the phase diagram of the
one-dimensional Hubbard model with asymmetric hopping coefficients and balanced
species. In the attractive regime we present a numerical study of the passage
from on-site pairing dominant correlations at small asymmetries to
charge-density waves in the region with markedly different hopping
coefficients. In the repulsive regime we exploit two analytical treatments in
the strong- and weak-coupling regimes in order to locate the onset of phase
separation at small and large asymmetries respectively.Comment: 13 pages, RevTeX 4, 12 eps figures, some additional refs. with
respect to v1 and citation errors fixe
Estimating Quasi-long-range Order via Renyi Entropies
We show how entanglement entropies allow for the estimation of
quasi-long-range order in one dimensional systems whose low-energy physics is
well captured by the Tomonaga-Luttinger liquid universality class. First, we
check our procedure in the exactly solvable XXZ spin-1/2 chain in its entire
critical region, finding very good agreement with Bethe ansatz results. Then,
we show how phase transitions between different dominant orders may be
efficiently estimated by considering the superfluid-charge density wave
transition in a system of dipolar bosons. Finally, we discuss the application
of this method to multispecies systems such as the one dimensional Hubbard
model. Our work represent the first proof of a direct relationship between the
Luttinger parameter and R\'enyi entropies in both bosonics and fermionic
lattice models.Comment: v2: minimal changes, 6 pages, 7 figures, accepted for publication in
Phys. Rev.
Spontaneous Peierls dimerization and emergent bond order in one-dimensional dipolar gases
We investigate the effect of dipolar interactions in one-dimensional systems in connection with the possibility of observing exotic many-body effects with trapped atomic and molecular dipolar gases. By combining analytical and numerical methods, we show how the competition between short- and long-range interactions gives rise to frustrating effects which lead to the stabilization of spontaneously dimerized phases characterized by a bond ordering. This genuine quantum order is sharply distinguished from Mott and spin-density-wave phases, and can be unambiguously probed by measuring nonlocal order parameters via in situ imaging techniques
Gap scaling at Berezinskii-Kosterlitz-Thouless quantum critical points in one-dimensional Hubbard and Heisenberg models
We discuss how to locate critical points in the
Berezinskii-Kosterlitz-Thouless (BKT) universality class by means of
gap-scaling analyses. While accurately determining such points using gap
extrapolation procedures is usually challenging and inaccurate due to the
exponentially small value of the gap in the vicinity of the critical point, we
show that a generic gap-scaling analysis, including the effects of logarithmic
corrections, provides very accurate estimates of BKT transition points in a
variety of spin and fermionic models. As a first example, we show how the
scaling procedure, combined with density-matrix-renormalization-group
simulations, performs extremely well in a non-integrable spin- XXZ model,
which is known to exhibit strong finite-size effects. We then analyze the
extended Hubbard model, whose BKT transition has been debated, finding results
that are consistent with previous studies based on the scaling of the
Luttinger-liquid parameter. Finally, we investigate an anisotropic extended
Hubbard model, for which we present the first estimates of the BKT transition
line based on large-scale density-matrix-renormalization-group simulations. Our
work demonstrates how gap-scaling analyses can help to locate accurately and
efficiently BKT critical points, without relying on model-dependent scaling
assumptions.Comment: 8 pages, 7 figure
Critical properties and R\'enyi entropies of the spin-3/2 XXZ chain
We discuss entanglement and critical properties of the spin-3/2 XXZ chain in
its entire gapless region. Employing density-matrix renormalization group
calculations combined with different methods based on level spectroscopy,
correlation functions and entanglement entropies, we determine the sound
velocity and the Luttinger parameter of the model as a function of the
anisotropy parameter. Then, we focus on entanglement properties by
systematically studying the behavior of R\'enyi entropies under both open and
periodic boundary conditions, providing further evidence of recent findings
about entanglement entropies of excited states in conformal field theory.Comment: 8 pages, 10 figures; small text revisions and a new figure. Accepted
for publication in Phys. Rev.
Observation of chiral edge states with neutral fermions in synthetic Hall ribbons
Chiral edge states are a hallmark of quantum Hall physics. In electronic systems, they appear as a macroscopic consequence of the cyclotron orbits induced by a magnetic field, which are naturally truncated at the physical boundary of the sample. Here we report on the experimental realization of chiral edge states in a ribbon geometry with an ultracold gas of neutral fermions subjected to an artificial gauge field. By imaging individual sites along a synthetic dimension, encoded in the nuclear spin of the atoms, we detect the existence of the edge states and observe the edge-cyclotron orbits induced during quench dynamics. The realization of fermionic chiral edge states opens the door for edge state interferometry and the study of non-Abelian anyons in atomic systems
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