20,166 research outputs found
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
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
Effect of incommensurate disorder on the resonant tunneling through Majorana bound states on the topological superconductor chains
We study the transport through the Kitaev's chain with incommensurate
potentials coupled to two normal leads by the numerical operator method. We
find a quantized linear conductance of , which is independent to the
disorder strength and the gate voltage in a wide range, signaling the Majorana
bound states. While the incommensurate disorder suppresses the current at
finite voltage bias, and then narrows the linear response regime of the
curve which exhibits two plateaus corresponding to the superconducting gap and
the band edge respectively. The linear conductance abruptly drops to zero as
the disorder strength reaches the critical value with the
p-wave pairing amplitude, corresponding to the transition from the topological
superconducting phase to the Anderson localized phase. Changing the gate
voltage will also cause an abrupt drop of the linear conductance by driving the
chain into the topologically trivial superconducting phase, whose curve
exhibits an exponential shape.Comment: 9 pages, 7 figure
Many-body ground state localization and coexistence of localized and extended states in an interacting quasiperiodic system
We study the localization problem of one-dimensional interacting spinless
fermions in an incommensurate optical lattice, which changes from an extended
phase to a nonergoic many-body localized phase by increasing the strength of
the incommensurate potential. We identify that there exists an intermediate
regime before the system enters the many-body localized phase, in which both
the localized and extended many-body states coexist, thus the system is divided
into three different phases, which can be characterized by normalized
participation ratios of the many-body eigenstates and distributions of natural
orbitals of the corresponding one-particle density matrix. This is very
different from its noninterating limit, in which all eigenstaes undergo a
delocaliztion-localization transtion when the strength of the incommensurate
potential exceeds a critical value.Comment: 5 pages, 6 figure
Quantum criticality in disordered bosonic optical lattices
Using the exact Bose-Fermi mapping, we study universal properties of
ground-state density distributions and finite-temperature quantum critical
behavior of one-dimensional hard-core bosons in trapped incommensurate optical
lattices. Through the analysis of universal scaling relations in the quantum
critical regime, we demonstrate that the superfluid to Bose glass transition
and the general phase diagram of disordered hard-core bosons can be uniquely
determined from finite-temperature density distributions of the trapped
disordered system.Comment: 4 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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