Density and spin response functions in ultracold fermionic atom gases.
We propose a new method of detecting the onset of superfluidity in a two-component ultracold fermionic gas of atoms governed by an attractive short-range interaction. By studying the two-body correlation functions we find that a measurement of the momentum distribution of the density and spin-response functions allows one to access separately the normal and anomalous densities. The change in sign at low momentum transfer of the normal-ordered part of the density response function signals the transition between a BEC and a BCS regime, characterized by small and large pairs, respectively. This change in sign of the density response function represents an unambiguous signature of the BEC-to-BCS crossover. Spin rotational symmetry breaking due to the magnetic field, if observed, can be used to validate the one-channel model.
Mihaila
Bogdan
B
Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
Gaudio
Sergio
S
Blagoev
Krastan B
KB
Balatsky
Alexander V
AV
Littlewood
Peter B
PB
Smith
Darryl L
DL