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Observation of Fermi Polarons in a Tunable Fermi Liquid of Ultracold Atoms

André Schirotzek, Cheng-Hsun Wu, Ariel Sommer, and Martin W. Zwierlein
Phys. Rev. Lett. 102, 230402 – Published 8 June 2009
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Abstract

We have observed Fermi polarons, dressed spin-down impurities in a spin-up Fermi sea of ultracold atoms. The polaron manifests itself as a narrow peak in the impurities’ rf spectrum that emerges from a broad incoherent background. We determine the polaron energy and the quasiparticle residue for various interaction strengths around a Feshbach resonance. At a critical interaction, we observe the transition from polaronic to molecular binding. Here, the imbalanced Fermi liquid undergoes a phase transition into a Bose liquid, coexisting with a Fermi sea.

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  • Received 17 February 2009

DOI:https://doi.org/10.1103/PhysRevLett.102.230402

©2009 American Physical Society

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Swimming in the Fermi sea

Published 8 June 2009

The fermionic analog of a solid-state polaron (an electron surrounded by a cloud of phonons) has been created by dropping a spin-down atom into a Fermi sea of spin-up ultracold atoms.

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Authors & Affiliations

André Schirotzek, Cheng-Hsun Wu, Ariel Sommer, and Martin W. Zwierlein

  • Department of Physics, MIT-Harvard Center for Ultracold Atoms, and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

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Issue

Vol. 102, Iss. 23 — 12 June 2009

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