110 research outputs found
Vortex-hole duality: a unified picture of weak and strong-coupling regimes of bosonic ladders with flux
Two-leg bosonic ladders with flux harbor a remarkable vortex-hole duality
between the weak-coupling vortex lattice superfluids and strong-coupling
charge-density-wave crystals. The strong-coupling crystalline states, which are
realized in the vicinity of -flux, are independent of particle statistics,
and are related with the incompressible fractional quantum Hall states in the
thin-cylinder limit. These fully gapped ground states, away of -flux,
develop nonzero chiral (spin) currents. Contact-interacting quantum gases
permit exploration of this vortex-hole duality in experiments.Comment: 11 pages, 15 figure
Quantum phases of strongly-interacting bosons on a two-leg Haldane ladder
We study the ground-state physics of a single-component Haldane model on a
hexagonal two-leg ladder geometry with a particular focus on strongly
interacting bosonic particles. We concentrate our analysis on the regime of
less than one particle per unit-cell. As a main result, we observe several
Meissner-like and vortex-fluid phases both for a superfluid as well as a
Mott-insulating background. Furthermore, we show that for strongly interacting
bosonic particles an unconventional vortex-lattice phase emerges, which is
stable even in the regime of hardcore bosons. We discuss the mechanism for its
stabilization for finite interactions by a means of an analytical
approximation. We show how the different phases may be discerned by measuring
the nearest- and next-nearest-neighbor chiral currents as well as their
characteristic momentum distributions.Comment: 13 pages, 20 figure
Magnetic field induced band insulator to Mott insulator transformations in 4-component alkali fermions at half-filling
Under the influence of an external magnetic field and spin-changing
collisions, the band insulator (BI) state of one-dimensional (1D) s-wave
repulsively interacting 4-component fermions at half-filling transforms into
Mott insulator (MI) states with spontaneously broken translational symmetry: a
dimerized state for shallow lattices and a N{\'e}el state for deep lattices via
an intermediate topological state. Since a BI has vanishing entropy per
particle, these MI phases could be particularly inviting for experimental
realization under the similar conditions as those for K atoms [1],
provided the magnetic field is changed adiabatically.Comment: 5 eps figure
Current fidelity susceptibility and conductivity in one-dimensional lattice models with open and periodic boundary conditions
We study, both numerically and analytically, the finite size scaling of the
fidelity susceptibility \chi_{J} with respect to the charge or spin current in
one-dimensional lattice models, and relate it to the low-frequency behavior of
the corresponding conductivity. It is shown that in gapless systems with open
boundary conditions the leading dependence on the system size L stems from the
singular part of the conductivity and is quadratic, with a universal form
\chi_{J}= 7KL^2 \zeta(3)/2\pi^4 where K is the Luttinger liquid parameter. In
contrast to that, for periodic boundary conditions the leading system size
dependence is directly connected with the regular part of the conductivity
(giving alternative possibility to study low frequency behavior of the regular
part of conductivity) and is subquadratic, \chi_{J} \propto L^\gamma(K), (with
a K dependent constant \gamma) in most situations linear, \gamma=1. For open
boundary conditions, we also study another current-related quantity, the
fidelity susceptibility to the lattice tilt \chi_{P} and show that it scales as
the quartic power of the system size, \chi_{P}=31KL^4 \zeta(5)/8 u^2 \pi^6,
where u is the sound velocity. We comment on the behavior of the current
fidelity susceptibility in gapped phases, particularly in the topologically
ordered Haldane state.Comment: 11 pages, 7 eps figure
Density-Dependent Synthetic Gauge Fields Using Periodically Modulated Interactions
We show that density-dependent synthetic gauge fields may be engineered by
combining periodically modu- lated interactions and Raman-assisted hopping in
spin-dependent optical lattices. These fields lead to a density- dependent
shift of the momentum distribution, may induce superfluid-to-Mott insulator
transitions, and strongly modify correlations in the superfluid regime. We show
that the interplay between the created gauge field and the broken sublattice
symmetry results, as well, in an intriguing behavior at vanishing interactions,
characterized by the appearance of a fractional Mott insulator.Comment: 5 pages, 5 figure
Ultra-cold bosons in zig-zag optical lattices
Ultra-cold bosons in zig-zag optical lattices present a rich physics due to
the interplay between frustration, induced by lattice geometry, two-body
interaction and three-body constraint. Unconstrained bosons may develop chiral
superfluidity and a Mott-insulator even at vanishingly small interactions.
Bosons with a three-body constraint allow for a Haldane-insulator phase in
non-polar gases, as well as pair-superfluidity and density wave phases for
attractive interactions. These phases may be created and detected within the
current state of the art techniques.Comment: 8 pages, 9 figure
A Laplace Transform Method for Molecular Mass Distribution Calculation from Rheometric Data
Polydisperse linear polymer melts can be microscopically described by the
tube model and fractal reptation dynamics, while on the macroscopic side the
generalized Maxwell model is capable of correctly displaying most of the
rheological behavior. In this paper, a Laplace transform method is derived and
different macroscopic starting points for molecular mass distribution
calculation are compared to a classical light scattering evaluation. The
underlying assumptions comprise the modern understanding on polymer dynamics in
entangled systems but can be stated in a mathematically generalized way. The
resulting method is very easy to use due to its mathematical structure and it
is capable of calculating multimodal molecular mass distributions of linear
polymer melts
Spontaneous increase of magnetic flux and chiral-current reversal in bosonic ladders: Swimming against the tide
The interplay between spontaneous symmetry breaking in many-body systems, the
wavelike nature of quantum particles and lattice effects produces an
extraordinary behavior of the chiral current of bosonic particles in the
presence of a uniform magnetic flux defined on a two-leg ladder. While
non-interacting as well as strongly interacting particles, stirred by the
magnetic field, circulate along the system's boundary in the counterclockwise
direction in the ground state, interactions stabilize vortex lattices. These
states break translational symmetry, which can lead to a reversal of the
circulation direction. Our predictions could readily be accessed in quantum gas
experiments with existing setups or in arrays of Josephson junctions.Comment: 5 pages + 5 pages of supplementary materia
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