Mediated interactions between Fermi polarons and the role of impurity quantum statistics

Abstract

The notion of quasi-particles is essential for understanding the behaviour of complex many-body systems. A prototypical example of a quasi-particle, a polaron, is an impurity strongly interacting with a surrounding medium. Fermi polarons, created in a Fermi sea, provide a paradigmatic realization of this concept. As an inherent and important property such quasi-particles interact with each other via modulation of the medium. While quantum simulation experiments with ultracold atoms have significantly improved our understanding of individual polarons, the detection of their interactions has remained elusive in these systems. Here, we report the unambiguous observation of mediated interactions between Fermi polarons consisting of K impurities embedded in a Fermi sea of Li atoms. Our results confirm two landmark predictions of Landau's Fermi-liquid theory: the shift of the polaron energy due to mediated interactions, linear in the concentration of impurities, and its sign inversion with impurity quantum statistics. For weak to moderate interactions between the impurities and the medium, we find excellent agreement with the static (zero-momentum and energy) predictions of Fermi-liquid theory. For stronger impurity-medium interactions, we show that the observed behaviour at negative energies can be explained by a more refined many-body treatment including retardation and molecule formation

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Cited by in corpus (35)

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• Engineering impurity Bell states through coupling with a quantum bath
• Quantum master equation from the eigenstate thermalization hypothesis
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• Time-dependent nuclear energy-density functional theory toolkit for neutron star crust: Dynamics of a nucleus in a neutron superfluid
• Competing few-body correlations in ultracold Fermi polarons
• Exact results for heavy unitary Bose polarons
• Universal quantum dynamics of Bose polarons
• Boson-fermion pairing and condensation in two-dimensional Bose-Fermi mixtures
• Momentum-dependent quasiparticle properties of the Fermi polaron from the functional renormalization group
• Mass-gap description of heavy impurities in Fermi gases
• Dual Spectroscopy of Quantum Simulated Fermi-Hubbard Systems
• An experimental platform for studying the heteronuclear Efimov effect with an ultracold mixture of ${}^6$Li and ${}^{133}$Cs atoms
• Creation of a degenerate Bose-Bose mixture of erbium and lithium atoms
• Non-equilibrium dynamics and atom-pair coherence in strongly interacting Bose-Fermi mixtures
• Correlated decoherence and thermometry with mobile impurities in a 1D Fermi gas
• Tunable Fujita-Miyazawa-Type Three-Body Force in Ultracold Atoms
• Mechanical stability of resonant Bose-Fermi mixtures
• Dipole-Mode Spectrum and Hydrodynamic Crossover in a Resonantly Interacting Two-Species Fermion Mixture
• Medium-enhanced polaron repulsion in a dilute Bose mixture
• Exploring kinetically induced bound states in triangular lattices with ultracold atoms: spectroscopic approach
• Effective two- and three-body interactions between dressed impurities in a tilted double-well potential
• Resonantly enhanced superconductivity mediated by spinor condensates
• Efficient variational approach to the Fermi polaron problem in two dimensions, both in and out of equilibrium
• Polaronic dressing of bound states
• Complex-valued in-medium potential between heavy impurities in ultracold atoms
• Dissipationless tune-out trapping for a lanthanide-alkali quantum gas mixture
• Phenomenological model of decaying Bose polarons