ABSTRACT: We study the superfluid-to-Mott insulator transition of bosons in a two-legged ladder optical lattice of a type accessible
in current experiments on double-well optical lattices. The zero-temperature phase diagram is mapped out, with a focus on
its dependence upon interchain hopping and the tilt between double wells. We find that the unit-filling Mott phase exhibits
a nonmonotonic behavior as a function of the tilt parameter, producing a reentrant phase transition between the Mott insulator
and superfluid phases.
Laser Physics 04/2012; 18(3):318-321. · 3.61 Impact Factor
ABSTRACT: We investigate the stability of the first excited state, the so-called “π-state,” of Bose-Einstein condensates in a double-well
potential. From the condition of complex excitation energies, we determine the critical barrier height, above which the π-state
is dynamically unstable. We find that the critical barrier height decreases monotonically as the number of condensate atoms
increases. We also simulate the dynamics of the π-state by solving the time-dependent Gross-Pitaevskii equation. Our simulation
results show that the π-state in the dynamically unstable region exhibits distinctively different behavior from that in the
dynamically stable region.
Laser Physics 04/2012; 18(3):314-317. · 3.61 Impact Factor
ABSTRACT: We study the superfluid and insulating phases of bosons in double-well optical lattices, and focus on the specific example of a two-legged ladder, which is currently accessible in experiments. We obtain the zero-temperature phase diagram using both mean-field and time-evolving block decimation techniques. We find that the mean-field approach describes the correct phase boundaries only when the intrachain hopping is sufficiently small in comparison to the on-site repulsion. We show the dependence of the phase diagram on the interchain hopping or tilt between double wells. We find that the Mott-insulator phase at unit filling exhibits a nonmonotonic behavior as a function of the tilt parameter, producing a reentrant phase transition between Mott insulator and superfluid phases. Finally, we determine the critical point separating the insulating and superfluid phases at commensurate fillings, where the Berezinskii-Kosterlitz-Thouless transition occurs.
Phys. Rev. A. 10/2007; 76(4).
ABSTRACT: We investigate the Landau damping of Bogoliubov excitations in a dilute Bose gas moving in an optical lattice at a finite
temperature. Using a 1D tight-binding model, we explicitly obtain the Landau damping rate, the sign of which determines the
stability of the condensate. We find that the sign changes at a certain velocity, which is exactly the same as the critical
velocity determined by the Landau criterion of superfluidity. This coincidence reveals the microscopic mechanism of the Landau
Laser Physics 01/2007; 17(2):215-220. · 3.61 Impact Factor