Quantum phase diagram and time-of-flight absorption pictures of an ultracold Bose system in a square optical superlattice

¹ Department of Physics, Shanghai University - Shanghai 200444, PRC
² Qian Weichang College, Shanghai University - Shanghai 200444, PRC

^(a) yjiang@shu.edu.cn (corresponding author)

Received: 9 July 2015
Accepted: 14 January 2016

Abstract

In this letter, by the use of the generalized effective potential theory, with the help of the process chain approach under the framework of the Kato formulation of the perturbation expansion, we calculate out the quantum phase diagram up to the 8th order for an ultracold Bose system in a square optical superlattice. Based on these perturbative data, with the help of the linear fit extrapolation technique, more accurate results are obtained, which are in excellent agreement with recent Monte Carlo numerical results. Moreover, by employing the generalized re-summed Green's function method and cumulant expansion, the momentum distribution function of the system is also calculated analytically and the time-of-flight absorption pictures of the system are plotted.