Localization of a Bose-Einstein condensate in a bichromatic optical lattice

TL;DR

This paper uses numerical simulations of the Gross-Pitaevskii equation to explore how a non-interacting and interacting Bose-Einstein condensate localizes in a one-dimensional bichromatic optical lattice, analyzing effects of potential parameters and interactions.

Contribution

It provides a detailed numerical study of BEC localization in bichromatic optical lattices, including effects of potential variation and atom interactions, extending previous experimental findings.

Findings

Localization depends on optical amplitudes and wavelengths.

Nonlinear interactions can destroy localization.

Simulated dynamics match experimental observations.

Abstract

By direct numerical simulation of the time-dependent Gross-Pitaevskii equation we study different aspects of the localization of a non-interacting ideal Bose-Einstein condensate (BEC) in a one-dimensional bichromatic quasi-periodic optical-lattice potential. Such a quasi-periodic potential, used in a recent experiment on the localization of a BEC [Roati et al., Nature 453, 895 (2008)], can be formed by the superposition of two standing-wave polarized laser beams with different wavelengths. We investigate the effect of the variation of optical amplitudes and wavelengths on the localization of a non-interacting BEC. We also simulate the non-linear dynamics when a harmonically trapped BEC is suddenly released into a quasi-periodic potential, {as done experimentally in a laser speckle potential [Billy et al., Nature 453, 891 (2008)]$ We finally study the destruction of the localization in an interacting BEC due to the repulsion generated by a positive scattering length between the bosonic atoms.