title: Extracting the condensate density from projection experiments with Fermi gases.
abstract: A debated issue in the physics of the BCS-BEC crossover with trapped Fermi atoms is to identify characteristic properties of the superfluid phase. Recently, a condensate fraction was measured on the BCS side of the crossover by sweeping the system in a fast (nonadiabatic) way from the BCS to the Bose-Einstein condensation (BEC) sides, thus "projecting" the initial many-body state onto a molecular condensate. We analyze here the theoretical implications of these projection experiments, by identifying the appropriate quantum-mechanical operator associated with the measured quantities and relating them to the many-body correlations occurring in the BCS-BEC crossover. Calculations are presented over wide temperature and coupling ranges, by including pairing fluctuations on top of the mean field.
authors.affiliation: Dipartimento di Fisica, Università di Camerino, I-62032 Camerino, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Perali
authors.forename: P
authors.initials: P
authors.lastname: Pieri
authors.forename: G C
authors.initials: GC
authors.lastname: Strinati