University of Cambridge > > Irregular seminars in TCM > Metastability and Coherence of Repulsive Polarons in a Strongly Interacting Fermi Mixture

Metastability and Coherence of Repulsive Polarons in a Strongly Interacting Fermi Mixture

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We investigate theoretically and experimentally the properties of a strongly-interacting mixture of 40K and 6Li fermionic atoms, in the limit where few potassium atoms may be considered as impurities in a large Fermi sea of degenerate lithium atoms. Experimentally, we use rf spectroscopy to map out the complete excitation spectrum of the “impurity problem”, which contains two well-defined quasi-particles, the attractive polaron at negative energies and the metastable repulsive polaron at positive energies, in addition to a broad molecule-hole continuum. We measure quasiparticle energies, lifetimes, and residues, finding excellent agreement with a theory which explicitly includes the finite range of the Feshbach resonance. Interestingly, we find that the presence of a large range (of order the interparticle spacing) substantially increases the lifetime of repulsive polarons, opening new perspectives for the investigation of gases with strong repulsive interactions.

This talk is part of the Irregular seminars in TCM series.

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