Beyond effective Hamiltonians: micromotion of Bose Einstein condensates in periodically driven optical lattices

TL;DR

This paper studies the micromotion effects in a Bose Einstein condensate within a periodically driven optical lattice, revealing how fast phase oscillations influence atomic dynamics and potential renormalization.

Contribution

It introduces a detailed analysis of micromotion in driven BECs, highlighting its impact on the effective potential and dynamical processes like quenches.

Findings

Micromotion significantly affects atomic momentum distributions.

The averaged potential is renormalized but retains the same spatial period.

Micromotion influences the outcome of sudden potential changes.

Abstract

We investigate a Bose Einstein condensate held in a 1D optical lattice whose phase undergoes a fast oscillation using a statistical analysis. The averaged potential experienced by the atoms boils down to a periodic potential having the same spatial period but with a renormalized depth. However, the atomic dynamics also contains a \emph{micromotion} whose main features are revealed by a Kolmorogov-Smirnov analysis of the experimental momentum distributions. We furthermore discuss the impact of the micromotion on a quench process corresponding to a proper sudden change of the driving amplitude which reverses the curvature of the averaged potential.