Transition from a two-dimensional superfluid to a one-dimensional Mott insulator.

Department of Theoretical Physics, Royal Institute of Technology, AlbaNova, SE-106 91 Stockholm, Sweden.
Physical Review Letters (Impact Factor: 7.73). 10/2007; 99(11):110401. DOI: 10.1103/PHYSREVLETT.99.110401
Source: arXiv

ABSTRACT A two-dimensional system of atoms in an anisotropic optical lattice is studied theoretically. If the system is finite in one direction, it is shown to exhibit a transition between a two-dimensional superfluid and a one-dimensional Mott insulating chain of superfluid tubes. Monte Carlo simulations are consistent with the expectation that the phase transition is of Kosterlitz-Thouless type. The effect of the transition on experimental time-of-flight images is discussed.

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    ABSTRACT: We investigate the behavior of a two-dimensional array of Bose-Einstein condensate tubes described by means of a Bose-Hubbard Hamiltonian. Using a Wannier function expansion for the wave function in each tube, we compute the Bose-Hubbard parameters related to two different longitudinal potentials, periodic and quasiperiodic. We predict that —upon increasing the external potential strength along the direction of the tubes— the system can experience a re-entrant transition between a Mott insulating phase and the superfluid one.
    EPL (Europhysics Letters) 06/2010; 90(4):46001. DOI:10.1209/0295-5075/90/46001 · 2.27 Impact Factor
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    ABSTRACT: We compute the ground state phase diagram of the 2d Bose-Hubbard model with anisotropic hopping using quantum Monte Carlo simulations, connecting the 1d to the 2d system. We find that the tip of the lobe lies on a curve controlled by the 1d limit over the full anisotropy range while the universality class is always the same as in the isotropic 2d system. This behavior can be derived analytically from the lowest RG equations and has a form typical for the underlying Kosterlitz-Thouless transition in 1d. We also compute the phase boundary of the Mott lobe for strong anisotropy and compare it to the 1d system. Our calculations shed light on recent cold gas experiments monitoring the dynamics of an expanding cloud.

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