title: Direct observation of the phonon energy in a Bose-Einstein condensate by tomographic imaging.
abstract: The momentum and energy of phonons in a Bose-Einstein condensate are measured directly from a time-of-flight image by computerized tomography. We find that the same atoms that carry the momentum of the excitation also carry the excitation energy. The measured energy is in agreement with the Bogoliubov spectrum. Hydrodynamic simulations are performed which confirm our observation.
authors.affiliation: Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Roee
authors.initials: R
authors.lastname: Ozeri
authors.forename: Jeff
authors.initials: J
authors.lastname: Steinhauer
authors.forename: Nadav
authors.initials: N
authors.lastname: Katz
authors.forename: Nir
authors.initials: N
authors.lastname: Davidson