20,555 research outputs found
Hidden-symmetry-protected topological phases on a one-dimensional lattice
We demonstrate the existence of topologically nontrivial phase in a
one-dimensional fermionic lattice system subjected to synthetic gauge fields,
which is beyond the standard Altland-Zirnbauer classification of topological
insulators. The topological phase can be characterized by the presence of
degenerate zero-mode edge states or a quantized Berry phase of the occupied
Bloch band. By analyzing symmetries of the system, we identify that the
topological phase and zero-mode edge states are protected by two hidden
symmetries. An extended model with hidden symmetry breaking is also studied in
order to reveal the effect of hidden symmetries on the symmetry protected
topological phase.Comment: 6 pages, 5 figure
Preparation of stable excited states in an optical lattice via sudden quantum quench
We study how stable excited many-body states of the Bose-Hubbard model,
including both the gas-like state for strongly attractive bosons and bound
cluster state for repulsive bosons, can be produced with cold bosonic atoms in
an one-dimensional optical lattice. Starting from the initial ground states of
strongly interacting bosonic systems, we can achieve stable excited states of
the systems with opposite interaction strength by suddenly switching the
interaction to the opposite limit. By exactly solving dynamics of the
Bose-Hubbard model, we demonstrate that the produced excited state can be a
very stable dynamic state. This allows the experimental study of excited state
properties of ultracold atoms system in optical lattices.Comment: 5 pages, 4 figure
Phase diagram of frustrated mixed-spin ladders in the strong-coupling limit
We study the ground-state properties of frustrated Heisenberg ferrimagnetic
ladders with antiferromagnetic exchange interactions and two types of
alternating sublattice spins. In the limit of strong rung couplings, we show
that the mixed spin-1/2 and spin-1 ladders can be systematically mapped onto a
spin-1/2 Heisenberg model with additional next-nearest-neighbor exchanges. The
system is either in a ferrimagnetic state or in a critical spin-liquid state
depending on the competition between the spin exchanges along the legs and the
diagonal exchanges.Comment: 6 pages, 2 figur
Topological invariants for phase transition points of one-dimensional topological systems
We study topological properties of phase transition points of two
topologically non-trivial classes (D and DIII) in one dimension
by assigning a Berry phase defined on closed circles around the gap closing
points in the parameter space of momentum and a transition driving parameter.
While the topological property of the system is generally
characterized by a topological invariant, we identify that it
has a correspondence to the quantized Berry phase protected by the
particle-hole symmetry, and then give a proper definition of Berry phase to the
phase transition point. By applying our scheme to some specific models of class
D and DIII, we demonstrate that the topological phase transition can be well
characterized by the Berry phase of the transition point, which reflects the
change of Berry phases of topologically different phases across the phase
transition point.Comment: 6 pages, 5 figure
Quantum dynamics of repulsively bound atom pairs in the Bose-Hubbard model
We investigate the quantum dynamics of repulsively bound atom pairs in an
optical lattice described by the periodic Bose-Hubbard model both analytically
and numerically. In the strongly repulsive limit, we analytically study the
dynamical problem by the perturbation method with the hopping terms treated as
a perturbation. For a finite-size system, we numerically solve the dynamic
problem in the whole regime of interaction by the exact diagonalization method.
Our results show that the initially prepared atom pairs are dynamically stable
and the dissociation of atom pairs is greatly suppressed when the strength of
the on-site interaction is much greater than the tunneling amplitude, i.e., the
strongly repulsive interaction induces a self-localization phenomenon of the
atom pairs.Comment: 7 pages, 6 figures, significant changes mad
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