Broad Feshbach resonance with a large background scattering length in a fermionic atom-molecule mixture

TL;DR

This paper reports the discovery of a broad Feshbach resonance with a large background scattering length in an ultracold fermionic atom-molecule mixture, enabling exploration of strongly interacting systems with mass imbalance.

Contribution

It presents the first observation and characterization of a broad Feshbach resonance in a fermionic atom-molecule mixture with a large background scattering length.

Findings

Resonantly enhanced loss rates and elastic scattering cross sections measured.

Atom-molecule mixture enters hydrodynamic regime far from resonance.

Phase-locked oscillations due to hydrodynamic drag observed.

Abstract

We report the observation of a broad magnetic Feshbach resonance with a large background scattering length in an ultracold fermionic mixture of $^{23}$Na$^{40}$K molecules and $^{40}$K atoms, with both species prepared in their lowest hyperfine states. The Feshbach resonance is characterized by measuring resonantly enhanced loss rates and elastic scattering cross sections via cross-species thermalization. The large background scattering length can drive the atom-molecule mixture into the hydrodynamic regime when the magnetic field is far from the resonance. We observe that the center-of-mass motions of the atoms and molecules are phase-locked and oscillate with a common frequency due to hydrodynamic drag effects. This broad atom-molecule Feshbach resonance with its large background scattering length opens up a new avenue towards studying strongly interacting fermionic gases with mass imbalance.