A High Phase-Space Density Gas of NaCs Feshbach Molecules

TL;DR

This paper reports the creation and characterization of ultracold bosonic NaCs Feshbach molecules, achieving high phase-space density and demonstrating a pathway toward degenerate dipolar molecular gases.

Contribution

It presents the first creation of ultracold NaCs Feshbach molecules with detailed resonance characterization and demonstrates control over molecule formation across various conditions.

Findings

Achieved phase-space density near 0.1

Demonstrated molecule association at temperatures as low as 70 nK

Characterized Feshbach resonance using bound state spectroscopy

Abstract

We report on the creation of ultracold gases of bosonic Feshbach molecules of NaCs. The molecules are associated from overlapping gases of Na and Cs using a Feshbach resonance at 864.12(5) G. We characterize the Feshbach resonance using bound state spectroscopy, in conjunction with a coupled-channel calculation. By varying the temperature and atom numbers of the initial atomic mixtures, we demonstrate the association of NaCs gases over a wide dynamic range of molecule numbers and temperatures, reaching 70 nK for our coldest systems and a phase-space density near 0.1. This is an important stepping-stone for the creation of degenerate gases of strongly dipolar NaCs molecules in their absolute ground state.