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

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