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

More Information: We thank G. Bertaina, G. Bruun, X. Cui, T. Enss, O. Goulko, D. Petrov, S. Pilati, N. Prokof´ev, B. Svistunov, H. Zhai, and the LENS Quantum Gases group for useful discussions and R. Grimm and J. Levinsen for a critical reading of the manuscript. This work was supported by the ERC through Grants No. 307032 QuFerm2D and No. 637738 PoLiChroM and through the EU H2020 Marie Sklodowska-Curie program (Grant No. 705269 SCOUTFermi2D to F. S.). P. M. acknowledges funding from a “Ramon y Cajal” fellowship, from MINECO (Severo Ochoa SEV-2015-0522 and FOQUS FIS2013-46768), Generalitat de Catalunya (SGR 874), and the Fundacio Privada Cellex.
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: 191
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