title: High sensitivity phonon spectroscopy of Bose-Einstein condensates using matter-wave interference.
abstract: We study low-momentum excitations of a Bose-Einstein condensate using a novel matter-wave interference technique. In time-of-flight expansion images we observe strong matter-wave fringe patterns. The fringe visibility is a sensitive spectroscopic probe of in-trap phonons and is explained by use of a Bogoliubov excitation projection method applied to the rescaled order parameter of the expanding condensate. Gross-Pitaevskii simulations agree with the experimental data and confirm the validity of the theoretical interpretation. We show that the high sensitivity of this detection scheme gives access to the quantized quasiparticle regime.
authors.affiliation: Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: N
authors.initials: N
authors.lastname: Katz
authors.forename: R
authors.initials: R
authors.lastname: Ozeri
authors.forename: J
authors.initials: J
authors.lastname: Steinhauer
authors.forename: N
authors.initials: N
authors.lastname: Davidson
authors.forename: C
authors.initials: C
authors.lastname: Tozzo
authors.forename: F
authors.initials: F
authors.lastname: Dalfovo