Probing Sound Speed of an Optically-Trapped Bose Gas with Periodically Modulated Interactions by Bragg Spectroscopy

TL;DR

This paper investigates how periodically modulated interactions influence the sound speed in a Bose-Einstein condensate trapped in an optical lattice, using numerical, analytical methods, and proposing experimental verification via Bragg spectroscopy.

Contribution

It demonstrates that PMI significantly alters the sound speed in a BEC and provides a framework for experimental probing through the dynamic structure factor and Bragg spectroscopy.

Findings

PMI strongly modifies the sound speed of a BEC.

Effects of PMI can be observed via the dynamic structure factor.

Predictions can be tested using Bragg spectroscopy.

Abstract

A Bose-Einstein condensate (BEC) with periodically modulated interactions (PMI) has emerged as a novel kind of periodic superfluid, which has been recently experimentally created using optical Feshbach resonance. In this paper, we are motivated to investigate the superfluidity of a BEC with PMI trapped in an optical lattice (OL). In particular, we explore the effects of PMI on the sound speed and the dynamical structure factor of the model system. Our numerical results, combined with the analytical results in both the weak-potential limit and the tight-binding limit, have shown that the PMI can strongly modify the sound speed of a BEC. Moreover, we have shown that the effects of PMI on sound speed can be experimentally probed via the dynamic structure factor, where the excitation strength toward the first Bogoliubov band exhibits marked difference from the non- PMI one. Our predictions of the effects of PMI on the sound speed can be tested using the Bragg spectroscopy.