title: Scale invariance and viscosity of a two-dimensional Fermi gas.
abstract: We investigate collective excitations of a harmonically trapped two-dimensional Fermi gas from the collisionless (zero sound) to the hydrodynamic (first sound) regime. The breathing mode, which is sensitive to the equation of state, is observed with an undamped amplitude at a frequency 2 times the dipole mode frequency for a large range of interaction strengths and different temperatures. This provides evidence for a dynamical SO(2,1) scaling symmetry of the two-dimensional Fermi gas. Moreover, we investigate the quadrupole mode to measure the shear viscosity of the two-dimensional gas and study its temperature dependence.
authors.affiliation: Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Enrico
authors.initials: E
authors.lastname: Vogt
authors.forename: Michael
authors.initials: M
authors.lastname: Feld
authors.forename: Bernd
authors.initials: B
authors.lastname: Fröhlich
authors.forename: Daniel
authors.initials: D
authors.lastname: Pertot
authors.forename: Marco
authors.initials: M
authors.lastname: Koschorreck
authors.forename: Michael
authors.initials: M
authors.lastname: Köhl