Strongly dipolar gases in a one-dimensional lattice: Bloch oscillations and matter-wave localization

TL;DR

This study investigates how quantum fluctuations influence the behavior of strongly dipolar Bose-Einstein condensates in a one-dimensional lattice, revealing long-lived Bloch oscillations and a transition to localized states driven by interactions.

Contribution

The paper introduces a discrete extended Gross-Pitaevskii model that incorporates quantum fluctuations to accurately describe dipolar gases in a lattice, highlighting new phases like macrodroplets and solitons.

Findings

Observation of long-lived Bloch oscillations in extended macrodroplets

Detection of a transition to interaction-driven localized states

Quantitative agreement between theory and experiment for various phases

Abstract

Three-dimensional quantum gases of strongly dipolar atoms can undergo a crossover from a dilute gas to a dense macrodroplet, stabilized by quantum fluctuations. Adding a one-dimensional optical lattice creates a platform where quantum fluctuations are still unexplored, and a rich variety of new phases may be observable. We employ Bloch oscillations as an interferometric tool to assess the role quantum fluctuations play in an array of quasi-two-dimensional Bose-Einstein condensates. Long-lived oscillations are observed when the chemical potential is balanced between sites, in a region where a macrodroplet is extended over several lattice sites. Further, we observe a transition to a state that is localized to a single lattice plane$-$driven purely by interactions$-$marked by the disappearance of the interference pattern in the momentum distribution. To describe our observations, we develop a discrete one-dimensional extended Gross-Pitaevskii theory, including quantum fluctuations and a variational approach for the on-site wavefunction. This model is in quantitative agreement with the experiment, revealing the existence of single and multisite macrodroplets, and signatures of a two-dimensional bright soliton.