20,367 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
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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