Bosons in optical lattices - from the Mott transition to the Tonks-Girardeau gas

S. Wessel, F. Alet, S. Trebst, D. Leumann, M. Troyer, G. George Batrouni

Published 2004-11-18, updated 2004-12-21Version 2

We present results from quantum Monte Carlo simulations of trapped bosons in optical lattices, focusing on the crossover from a gas of softcore bosons to a Tonks-Girardeau gas in a one-dimensional optical lattice. We find that depending on the quantity being measured, the behavior found in the Tonks-Girardeau regime is observed already at relatively small values of the interaction strength. A finite critical value for entering the Tonks-Girardeau regime does not exist. Furthermore, we discuss the computational efficiency of two quantum Monte Carlo methods to simulate large scale trapped bosonic systems: directed loops in stochastic series expansions and the worm algorithm.