title: Clock shift in a strongly interacting two-dimensional Fermi gas.
abstract: We derive universal relations for the rf spectroscopy of a two-dimensional Fermi gas consisting of two spin states interacting through an S-wave scattering length. The rf transition rate has a high-frequency tail that is proportional to the contact and displays logarithmic scaling violations, decreasing asymptotically like 1/(ω2ln2ω). Its coefficient is proportional to ln2'(a'(2D)/a(2D)), where a(2D) and a'(2D) are the two-dimensional scattering lengths associated with initial-state and final-state interactions. The clock shift is proportional to the contact and to ln(a'(2D)/a(2D)). If |ln(a'(2D)/a(2D))| >> 1, the clock shift arises as a cancellation between much larger contributions proportional to ln2(a'(2D)/a(2D)) from bound-bound and bound-free rf transitions.
authors.affiliation: Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Langmack
authors.forename: Marcus
authors.initials: M
authors.lastname: Barth
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Zwerger
authors.forename: Eric
authors.initials: E
authors.lastname: Braaten