Spectroscopic signatures of nonequilibrium pairing in atomic fermi gases.
We determine the radio-frequency (rf) spectra for nonstationary states of a fermionic condensate produced by a rapid switch of the scattering length. The rf spectrum of the nonequilibrium state with constant BCS order parameter has two features in contrast with equilibrium where there is a single peak. The additional feature reflects the presence of excited pairs in the steady state. In the state characterized by periodically oscillating order parameter, the rf-absorption spectrum contains two sequences of peaks spaced by the frequency of oscillations. Satellite peaks appear due to a process where a rf photon in addition to breaking a pair emits or absorbs oscillation quanta.
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Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA.
Yuzbashyan
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Altshuler
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Coleman
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