title: Temperature dependence of the universal contact parameter in a unitary Fermi gas.
abstract: The contact I, introduced by Tan, has emerged as a key parameter characterizing universal properties of strongly interacting Fermi gases. For ultracold Fermi gases near a Feshbach resonance, the contact depends upon two quantities: the interaction parameter 1/(k(F)a), where k(F) is the Fermi wave vector and a is the s-wave scattering length, and the temperature T/T(F), where T(F) is the Fermi temperature. We present the first measurements of the temperature dependence of the contact in a unitary Fermi gas using Bragg spectroscopy. The contact is seen to follow the predicted decay with temperature and shows how pair-correlations at high momentum persist well above the superfluid transition temperature.
authors.affiliation: ARC Centre of Excellence for Quantum-Atom Optics, Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122, Australia.
authors.forename: E D
authors.initials: ED
authors.lastname: Kuhnle
authors.forename: S
authors.initials: S
authors.lastname: Hoinka
authors.forename: P
authors.initials: P
authors.lastname: Dyke
authors.forename: H
authors.initials: H
authors.lastname: Hu
authors.forename: P
authors.initials: P
authors.lastname: Hannaford
authors.forename: C J
authors.initials: CJ
authors.lastname: Vale