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

TL;DR

This paper presents a detailed theoretical analysis of an ultracold Bose system in a square optical superlattice, including phase diagram calculations and momentum distribution predictions, validated against numerical results.

Contribution

It introduces a combined perturbative and Green's function approach to accurately determine the phase diagram and momentum distribution of the system.

Findings

Quantum phase diagram calculated up to 8th order with high accuracy.

Analytical momentum distribution functions match Monte-Carlo results.

Time-of-flight images predicted for experimental verification.

Abstract

In this letter, by the use of the generalized effective potential theory, with the help of process-chain approach under the framework of Kato formulation of perturbation expansion, we calculate out the quantum phase diagram up to 8-th order for an ultracold Bose system in a square optical superlattice. Base on these perturbative data, with the help of the linear fit extrapolation technique, more accurate results are gotten, 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.