Phase diagram of quasi-two-dimensional bosons in laser speckle potential

TL;DR

This paper investigates the phase diagram of a quasi-two-dimensional Bose gas with laser speckle disorder, identifying a superfluid-insulator transition and deriving analytical expressions for key properties.

Contribution

It provides a combined theoretical and numerical analysis of disorder effects on Bose gases, including new analytical formulas and critical parameters for phase transitions.

Findings

Superfluid to insulator transition with increasing disorder strength

Analytical expressions for zero-momentum and superfluid fractions in weak disorder

Comparison of critical parameters with percolation theory predictions

Abstract

We have studied the phase diagram of a quasi-two-dimensional interacting Bose gas at zero temperature in the presence of random potential created by laser speckles. The superfluid fraction and the fraction of particles with zero momentum are obtained within the mean-field Gross-Pitaevskii theory and in diffusion Monte Carlo simulations. We find a transition from the superfluid to the insulating state, when the strength of the disorder grows. Estimations of the critical parameters are compared with the predictions of the percolation theory in the Thomas-Fermi approximation. Analytical expressions for the zero-momentum fraction and the superfluid fraction are derived in the limit of weak disorder and weak interactions within the framework of the Bogoliubov theory. Limits of validity of various approximations are discussed.