Quantum Engineering of a Low-Entropy Gas of Heteronuclear Bosonic Molecules in an Optical Lattice

TL;DR

This paper presents a versatile method for creating low-entropy, ultracold heteronuclear molecules in an optical lattice, enabling advanced quantum many-body physics experiments with long-range interactions.

Contribution

It introduces a novel technique for mixing two-species quantum gases in an optical lattice to produce high-filling, low-entropy heteronuclear molecules.

Findings

Achieved over 30% lattice filling fraction of RbCs molecules.

Produced a dense sample of more than 5000 ultracold molecules.

Demonstrated efficient atom pairing via superfluid-to-Mott insulator transitions.

Abstract

We demonstrate a generally applicable technique for mixing two-species quantum degenerate bosonic samples in the presence of an optical lattice, and we employ it to produce low-entropy samples of ultracold 87Rb133Cs Feshbach molecules with a lattice filling fraction exceeding 30%. Starting from two spatially separated Bose-Einstein condensates of Rb and Cs atoms, Rb-Cs atom pairs are efficiently produced by using the superfluid-to-Mott insulator quantum phase transition twice, first for the Cs sample, then for the Rb sample, after nulling the Rb-Cs interaction at a Feshbach resonance's zero crossing. We form molecules out of atom pairs and characterize the mixing process in terms of sample overlap and mixing speed. The dense and ultracold sample of more than 5000 RbCs molecules is an ideal starting point for experiments in the context of quantum many-body physics with long-range dipolar interactions.