Lifetime of Feshbach dimers in a Fermi-Fermi mixture of $^6$Li and $^{40}$K

TL;DR

This study combines experiments and theory to analyze the lifetime of weakly bound Feshbach dimers in a $^6$Li-$^{40}$K mixture, revealing suppression of collisional losses near narrow resonances and providing predictive models for similar systems.

Contribution

It offers the first combined experimental and theoretical analysis of dimer lifetimes in mass-imbalanced Fermi mixtures near narrow Feshbach resonances, extending understanding beyond broad resonance cases.

Findings

Loss processes are suppressed near the Feshbach resonance.

Theoretical predictions match experimental measurements.

Model calculations suggest broader applicability to other systems.

Abstract

We present a joint experimental and theoretical investigation of the lifetime of weakly bound dimers formed near narrow interspecies Feshbach resonances in mass-imbalanced Fermi-Fermi systems, considering the specific example of a mixture of $^6$Li and $^{40}$K atoms. Our work addresses the central question of the increase in the stability of the dimers resulting from Pauli suppression of collisional losses, which is a well-known effect in mass-balanced fermionic systems near broad resonances. We present measurements of the spontaneous dissociation of dimers in dilute samples, and of the collisional losses in dense samples arising from both dimer-dimer processes and from atom-dimer processes. We find that all loss processes are suppressed close to the Feshbach resonance. Our general theoretical approach for fermionic mixtures near narrow Feshbach resonances provides predictions for the suppression of collisional decay as a function of the detuning from resonance, and we find excellent agreement with the experimental benchmarks provided by our $^6$Li-$^{40}$K system. We finally present model calculations for other Feshbach-resonant Fermi-Fermi systems, which are of interest for experiments in the near future.