Localization and Anomalous Transport in a 1-D Soft Boson Optical Lattice

TL;DR

This paper investigates how Bose-Einstein condensates in a 1-D optical lattice exhibit localization and transport suppression when collective tunneling and interaction energies are comparable, revealing quantum fluctuation effects.

Contribution

It provides experimental evidence of quantum fluctuation induced localization in a 1-D optical lattice with mesoscopic atom numbers, and analyzes transport behavior near the localization threshold.

Findings

Transport suppression at a critical energy ratio

Observation of superfluid transport frequency deviations

Evidence of quantum fluctuation induced localization

Abstract

We study the dynamics of Bose-Einstein condensed atoms in a 1-D optical lattice potential in a regime where the collective (Josephson) tunneling energy is comparable with the on-site interaction energy, and the number of particles per lattice site is mesoscopically large. By directly imaging the motion of atoms in the lattice, we observe an abrupt suppression of atom transport through the array for a critical ratio of these energies, consistent with quantum fluctuation induced localization. Directly below the onset of localization, the frequency of the observed superfluid transport can be explained by a phonon excitation but deviates substantially from that predicted by the hydrodynamic/Gross-Pitaevskii equations.