182 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
Topological quasi-one-dimensional state of interacting spinless electrons
By decreasing the transversal confinement potential in interacting
one-dimensional spinless electrons and populating the second energetically
lowest sub-band, for not too strong interactions system transitions into a
quasi-one-dimensional state with dominant superconducting correlations and one
gapless mode. By combining effective field theory approach and numerical
density matrix renormalization group simulations we show that this
quasi-one-dimensional state is a topological state that hosts zero-energy edge
modes. We also study the single-particle correlations across the interface
between this quasi-one-dimensional and single-channel states.Comment: 8 pages, 10 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
Magnetic phases of spin-3/2 fermions on a spatially anisotropic square lattice
We study the magnetic phase diagram of spin-3/2 fermions in a spatially
anisotropic square optical lattice at quarter filling (corresponding to one
particle per lattice site). In the limit of the large on-site repulsion the
system can be mapped to the so-called Sp(N) Heisenberg spin model with N=4. We
analyze the Sp(N) spin model with the help of the large-N field-theoretical
approach and show that the effective theory corresponds to the Sp(N) extension
of the CP^{N-1} model, with the Lorentz invariance generically broken. We
obtain the renormalization flow of the model couplings and show that although
the Sp(N) terms are seemingly irrelevant, their presence leads to a
renormalization of the CP^{N-1} part of the action, driving a phase transition.
We further consider the influence of the external magnetic field (the quadratic
Zeeman effect), and present the qualitative analysis of the ground state phase
diagram.Comment: 10 Revtex pages, 5 figures; (v2) corrected the last paragraph in
Appendix B and some typos; (v3) added references, extended discussion of the
phase diagra
Ground-state phases of rung-alternated spin-1/2 Heisenberg ladder
The ground-state phase diagram of Heisenberg spin-1/2 system on a two-leg
ladder with rung alternation is studied by combining analytical approaches with
numerical simulations. For the case of ferromagnetic leg exchanges a unique
ferrimagnetic ground state emerges, whereas for the case of antiferromagnetic
leg exchanges several different ground states are stabilized depending on the
ratio between exchanges along legs and rungs. For the more general case of a
honeycomb-ladder model for the case of ferromagnetic leg exchanges besides
usual rung-singlet and saturated ferromagnetic states we obtain a ferrimagnetic
Luttinger liquid phase with both linear and quadratic low energy dispersions
and ground state magnetization continuously changing with system parameters.
For the case of antiferromagnetic exchanges along legs, different dimerized
states including states with additional topological order are suggested to be
realized
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
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