448 research outputs found
Exotic Haldane Superfluid Phase of Soft-Core Bosons in Optical Lattices
We propose to realize an exotic Haldane superfluid (HSF) phase in an extended
Bose-Hubbard model on the two-leg ladder (i.e., a two-species mixture of
interacting bosons). The proposal is confirmed by means of large-scale quantum
Monte Carlo simulations, with a significant part of the ground-state phase
diagram being revealed. Most remarkably, the newly discovered HSF phase
features both superfluidity and the non-local topological Haldane order. The
effects induced by varying the number of legs are furthermore explored. Our
results shed light on how topological superfluid emerges in bosonic systems.Comment: 5 pages, 6 figures; accepted for publication in Physical Review B
(April 29, 2016
Bosonic Haldane insulator in the presence of local disorder: A quantum Monte Carlo study
The Haldane phase (HP) is a paradigmatic example of symmetry protected
topological phase. We explore how the bosonic HP behaves in the presence of
local disorder, employing quantum Monte Carlo simulations of an extended
Bose-Hubbard model subject to uncorrelated, quenched disorders. We find that
the HP is robust against a weak disorder and the non-local string order of HP
exhibits a reentrant behavior. Besides, a direct transition between the HP and
superfluid phase is uncovered. A significant part of the ground-state phase
diagram is established for the model, unveiling the location of HP surrounded
by Bose glass, charge density wave and superfluid phases. We also mention a
possible experimental scheme with optical lattice emulator to realize the
present findings.Comment: 6 pages, 5 figure
Flux-lattice melting in LaOFFeAs: first-principles prediction
We report the theoretical study of the flux-lattice melting in the novel
iron-based superconductor and
. Using the Hypernetted-Chain closure and an
efficient algorithm, we calculate the two-dimensional one-component plasma pair
distribution functions, static structure factors and direct correlation
functions at various temperatures. The Hansen-Verlet freezing criterion is
shown to be valid for vortex-liquid freezing in type-II superconductors.
Flux-lattice meting lines for and
are predicted through the combination of the density
functional theory and the mean-field substrate approach.Comment: 5 pages, 4 figures, to appear in Phys. Rev.
Phase transition in site-diluted Josephson junction arrays: A numerical study
We numerically investigate the intriguing effects produced by random
percolative disorder in two-dimensional Josephson-junction arrays. By dynamic
scaling analysis, we evaluate critical temperatures and critical exponents with
high accuracy. It is observed that, with the introduction of site-diluted
disorder, the Kosterlitz-Thouless phase transition is eliminated and evolves
into a continuous transition with power-law divergent correlation length.
Moreover, genuine depinning transition and creep motion are studied, evidence
for distinct creep motion types is provided. Our results not only are in good
agreement with the recent experimental findings, but also shed some light on
the relevant phase transitions.Comment: 7 pages, 8 figures, Phys. Rev. B (in press
Dynamics of glass phases in the two-dimensional gauge glass model
Large-scale simulations have been performed on the current-driven
two-dimensional XY gauge glass model with resistively-shunted-junction
dynamics. It is observed that the linear resistivity at low temperatures tends
to zero, providing strong evidence of glass transition at finite temperature.
Dynamic scaling analysis demonstrates that perfect collapses of current-voltage
data can be achieved with the glass transition temperature , the
correlation length critical exponent , and the dynamic critical
exponent . A genuine continuous depinning transition is found at zero
temperature. For creeping at low temperatures, critical exponents are evaluated
and a non-Arrhenius creep motion is observed in the glass phase.Comment: 10 pages, 6 figure
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