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SUMMARY:Metastability and Coherence of Repulsive Polarons in a Strongly In
 teracting Fermi Mixture - Dr. Pietro Massignan\, ICFO - The Institute of P
 hotonic Sciences\, Barcelona\, Spain
DTSTART:20111215T141500Z
DTEND:20111215T151500Z
UID:TALK34895@talks.cam.ac.uk
CONTACT:Joe Bhaseen
DESCRIPTION:We investigate theoretically and experimentally the properties
  of a strongly-interacting mixture of 40K and 6Li fermionic atoms\, in the
  limit where few potassium atoms may be considered as impurities in a larg
 e Fermi sea of degenerate lithium atoms. Experimentally\, we use rf spectr
 oscopy to map out the complete excitation spectrum of the "impurity proble
 m"\, which contains two well-defined quasi-particles\, the attractive pola
 ron at negative energies and the metastable repulsive polaron at positive 
 energies\, in addition to a broad molecule-hole continuum. We measure quas
 iparticle energies\, lifetimes\, and residues\, finding excellent agreemen
 t with a theory which explicitly includes the finite range of the Feshbach
  resonance. Interestingly\, we find that the presence of a large range (of
  order the interparticle spacing) substantially increases the lifetime of 
 repulsive polarons\, opening new perspectives for the investigation of gas
 es with strong repulsive interactions.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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