Superfluidity of Two–Dimensional and One–Dimensional Systems

Victor Nikolaevich Popov

D. J. Bishop

Sara Bergkvist, Anders Rosengren, Robert Saers +3 more

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.

F.W. Cummings, James R. Johnston

Krešimir Dželalija

The properties of interacting ultracold Bose systems were investigated using quantum Monte Carlo simulations. The superfluidity and Bose-Einstein condensation of very dilute two species trapped bosons mixtures as a function of temperature were investigated. Depending on the interactions, the system can be in three different modes: mixed, separated into two blobs, and separated in a shell regime. Anisotropy of superfluidity was observed in the case of two blobs. A transition was also observed in which the superfluidity fraction becomes smaller than the condensate fraction for each regime. We further investigated the properties of one dimensional strongly interacting bosonic systems in periodic potentials. The transition of the superfluid to the Mott insulator phase in the robust and fragile superfluid regimes is shown in detail. We investigated transition from a one-dimensional system to a two-dimensional one of helium-4 in the nanopore. We analyzed the scaling of the helium-4 superfluidity with the product of the temperature and the length of the simulation cell and the agreement of the results with the theoretical predictions. The transition of the helium-4 system from one-dimensional to two-dimensional with an increase in the linear density within the nanopores of radius R = 4 A was observed, which is visible in the behavior of the correlation function and suprafluidity.

Tobias Dornheim, Alexey V. Filinov, M. Bönitz