Ultracold and dense samples of ground-state molecules in lattice potentials

TL;DR

This paper reports the creation of ultracold, dense samples of ground-state Cs_2 molecules in an optical lattice, with long lifetimes and high transfer efficiency, advancing the pursuit of molecular Bose-Einstein condensates and dipolar quantum gases.

Contribution

It demonstrates a method to produce and transfer ultracold molecules to their ground state with high efficiency in a lattice, a key step for quantum many-body physics.

Findings

Molecules are trapped in the motional ground state with 8 s lifetime.

Achieved >50% transfer efficiency to the ground state.

Produced a dense, near-degenerate molecular sample.

Abstract

We produce an ultracold and dense sample of rovibronic ground state Cs_2 molecules close to the regime of quantum degeneracy, in a single hyperfine level, in the presence of an optical lattice. The molecules are individually trapped, in the motional ground state of an optical lattice well, with a lifetime of 8 s. For preparation, we start with a zero-temperature atomic Mott-insulator state with optimized double-site occupancy and efficiently associate weakly-bound dimer molecules on a Feshbach resonance. Despite extremely weak Franck-Condon wavefunction overlap, the molecules are subsequently transferred with >50% efficiency to the rovibronic ground state by a stimulated four-photon process. Our results present a crucial step towards the generation of Bose-Einstein condensates of ground-state molecules and, when suitably generalized to polar heteronuclear molecules such as RbCs, the realization of dipolar many-body quantum-gas phases in periodic potentials.