Quasiparticle Lifetime of the Repulsive Fermi Polaron

Haydn S. Adlong, Weizhe Edward Liu, Francesco Scazza, Matteo Zaccanti, Nelson Darkwah Oppong, Simon Fölling, Meera M. Parish, Jesper Levinsen

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Abstract

We investigate the metastable repulsive branch of a mobile impurity coupled to a degenerate Fermi gas via short-range interactions. We show that the quasiparticle lifetime of this repulsive Fermi polaron can be experimentally probed by driving Rabi oscillations between weakly and strongly interacting impurity states. Using a time-dependent variational approach, we find that we can accurately model the impurity Rabi oscillations that were recently measured for repulsive Fermi polarons in both two and three dimensions. Crucially, our theoretical description does not include relaxation processes to the lower-lying attractive branch. Thus, the theory-experiment agreement demonstrates that the quasiparticle lifetime is dominated by many-body dephasing within the upper repulsive branch rather than by relaxation from the upper branch itself. Our findings shed light on recent experimental observations of persistent repulsive correlations, and have important consequences for the nature and stability of the strongly repulsive Fermi gas.

Original languageEnglish
Pages (from-to)133401
Number of pages1
JournalPhysical Review Letters
Volume125
Issue number13
DOIs
Publication statusPublished - 25 Sep 2020

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