Stable Bloch oscillations of cold atoms with time-dependent interaction

TL;DR

This paper demonstrates that harmonically modulated interactions can sustain Bloch oscillations in cold atoms, with stability predicted through collective coordinate analysis and Floquet theory, validated by numerical simulations.

Contribution

It introduces a method to stabilize Bloch oscillations via time-dependent interactions and provides a predictive framework for stability analysis.

Findings

Harmonic modulation can preserve Bloch oscillations.

Stability depends on modulation frequency and phase.

Floquet theory accurately predicts unstable modes.

Abstract

We investigate Bloch oscillations of interacting cold atoms in a mean-field framework. In general, atom-atom interaction causes dephasing and destroys Bloch oscillations. Here, we show that Bloch oscillations are persistent if the interaction is modulated harmonically with suitable frequency and phase. For other modulations, Bloch oscillations are rapidly damped. We explain this behavior in terms of collective coordinates whose Hamiltonian dynamics permits to predict a whole family of stable solutions. In order to describe also the unstable cases, we carry out a stability analysis for Bogoliubov excitations. Using Floquet theory, we are able to predict the unstable modes as well as their growth rate, found to be in excellent agreement with numerical simulations.