Out-of-equilibrium dynamics of a Bose Einstein condensate in a periodically driven band system

TL;DR

This paper investigates the out-of-equilibrium behavior of a Bose-Einstein condensate in a periodically driven optical lattice, revealing nucleation of staggered states and gap solitons through experimental and theoretical analysis.

Contribution

It demonstrates the nucleation of staggered states and gap solitons in a driven BEC, providing quantitative analysis and exploring quantum versus thermal fluctuation effects.

Findings

Nucleation of staggered states via four wave mixing.

Observation of gap solitons after the quench.

Quantitative agreement with a Truncated Wigner approach.

Abstract

We report on the out-of-equilibrium dynamics of a Bose-Einstein condensate (BEC) placed in an optical lattice whose phase is suddenly modulated. The frequency and the amplitude of modulation are chosen to ensure a negative renormalized tunneling rate. Under these conditions, staggered states are nucleated by a spontaneous four wave mixing mechanism. The nucleation time is experimentally studied as a function of the renormalized tunnel rate, the atomic density and the modulation frequency. Our results are quantitatively well accounted for by a Truncated Wigner approach and reveal the nucleation of gap solitons after the quench. We discuss the role of quantum versus thermal fluctuations in the nucleation process and experimentally address the limit of the effective Hamiltonian approach.