Unstable regimes for a Bose-Einstein condensate in an optical lattice

TL;DR

This paper experimentally investigates energetic and dynamical instabilities in a Bose-Einstein condensate within a 1D optical lattice, distinguishing the regimes and comparing observations with theoretical models.

Contribution

It provides the first experimental separation of energetic and dynamical instability regimes in BECs in optical lattices, supported by theoretical analysis.

Findings

Identified clear separation between energetic and dynamical instabilities.

Measured timescales of instability-induced losses.

Validated theoretical models against experimental data.

Abstract

We report on the experimental characterization of energetic and dynamical instability, two mechanisms responsible for the breakdown of Bloch waves in a Bose-Einstein condensate interacting with a 1D optical lattice. A clear separation of these two regimes is obtained performing measurements at different temperatures of the atomic sample. The timescales of the two processes have been determined by measuring the losses induced in the condensate. A simple phenomenological model is introduced for energetic instability while a full comparison is made between the experiment and the 3D Gross-Pitaevskii theory that accounts for dynamical instability.