Polarons and dressed molecules near narrow Feshbach resonances
ICFO - The Institute of Photonic Sciences - 08860 Castelldefels (Barcelona), Spain, EU
Accepted: 9 March 2012
The properties of impurities immersed in a large Fermi sea are naturally described in terms of dressed quasiparticles: attractive and repulsive polarons, and dressed molecules. Motivated by recent experiments on narrow Feshbach resonances, we analyze here how the quasiparticle properties are affected by a non-zero resonance range. We find two interesting analytic results. For large range, the ground-state energy close to resonance is shown to become perturbative in the inverse range. In the limit of broad resonance instead, we provide a new Tan's relation linking the impurity ground-state energy E↓ to the number of atoms in its dressing cloud ΔN. As a corollary, at unitarity one finds ΔN=−E↓/ϵF, with ϵF the Fermi energy of the bath.
PACS: 03.75.Ss – Degenerate Fermi gases / 05.30.Fk – Fermion systems and electron gas / 71.10.Ca – Electron gas, Fermi gas
© EPLA, 2012