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.
- Received 17 February 2009
DOI:https://doi.org/10.1103/PhysRevLett.102.230402
©2009 American Physical Society
Viewpoint
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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