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: CNR, INO, I-50019 Sesto Fiorentino, Italy; Univ Florence, LENS, I-50019 Sesto Fiorentino, Italy; Univ Florence, Dipartimento Fis & Astron, I-50019 Sesto Fiorentino, Italy; Barcelona Inst Sci & Technol, ICFO Inst Ciencies Foton, Castelldefels 08860, Spain; Univ Trento, INO CNR BEC Ctr, I-38123 Povo, Italy; Univ Trento, Dipartimento Fis, I-38123 Povo, Italy; Ludwig Maximilians Univ Munchen, D-80333 Munich, 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, Ež 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: 203
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