Ultracold ⁶Li-⁵³Cr Fermi mixtures with tunable interactions

Mass-imbalanced Fermi mixtures are expected to greatly enhance the observability of elusive regimes of highly-correlated fermionic matter, primarily in the context of unconventional superfluidity and quantum magnetism.

Here, we report on our progress towards novel ⁶Li-⁵³Cr degenerate Fermi mixtures. The peculiar mass ratio of our system uniquely enables the existence of resonant few-body cluster states with p-wave symmetry on the molecular side of an inter-species Feshbach resonance, together with an extraordinary suppression of three-body recombination processes at strong repulsion. These properties will allow us to resonantly tune elastic few-body p-wave interactions on top of the standard 2-body ones, as well as to overcome pairing instabilities in repulsive Fermi mixtures.

First, we will discuss our all-optical strategy to attain large ultracold samples of up to 10⁶ Li and 3 10⁵ Cr atoms at micro-Kelvin temperatures. Second, we will report on extensive Feshbach spectroscopy performed onto the six Li-Cr spin-mixtures of lowest energy. In particular, we identified more than 30 inter-species resonances, including four isolated features in the absolute mixture ground state, immune to two-body losses, and thereby promising for future many-body surveys.

[1] E. Neri et al., Phys. Rev. A 101, 063602 (2020)

[2] B. Bazak and D. S. Petrov, Phys. Rev. Lett. 118, 083002

[3] D. S. Petrov, Phys. Rev. A 67, 010703(R)