Repulsive Fermi Polarons in a Resonant Mixture of Ultracold 6Li Atoms

Year: 2017

Authors: Scazza F., Valtolina G., Massignan P., Recati A., Amico A., Burchianti A., Fort C., Inguscio M., Zaccanti M., Roati G.

Autors Affiliation: Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche (INO-CNR), 50019 Sesto Fiorentino, Italy; LENS and Dipartimento di Fisica e Astronomia, Università di Firenze, 50019 Sesto Fiorentino, Italy; ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels, Spain; INO-CNR BEC Center and Dipartimento di Fisica, Università di Trento, 38123 Povo, Italy; Ludwig-Maximilians-Universität München, 80333 München, Germany

Abstract: We employ radio-frequency spectroscopy to investigate a polarized spin mixture of ultracold 6Li atoms close to a broad Feshbach scattering resonance. Focusing on the regime of strong repulsive interactions, we observe well-defined coherent quasiparticles even for unitarity-limited interactions. We characterize the many-body system by extracting the key properties of repulsive Fermi polarons: the energy E+, the effective mass m*, the residue Z, and the decay rate Γ. Above a critical interaction, Eþ is found to exceed the Fermi energy of the bath, while m* diverges and even turns negative, thereby indicating that the repulsive Fermi liquid state becomes energetically and thermodynamically unstable.

Journal/Review: PHYSICAL REVIEW LETTERS

Volume: 118 (8)      Pages from: 083602-1  to: 083602-6

KeyWords: Fermi level; Fermi liquids; Polarons; Radiofrequency spectroscopy, Effective mass; Fermi liquid state; Many-body systems; Polarized spins; Quasiparticles; Repulsive interactions; Resonant mixtures; Scattering resonance, Mixtures; Ultracold fermions; Polarons
DOI: 10.1103/PhysRevLett.118.083602

Citations: 167
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