title: Detecting the amplitude mode of strongly interacting lattice bosons by Bragg scattering.
abstract: We report the first detection of the Higgs-type amplitude mode using Bragg spectroscopy in a strongly interacting condensate of ultracold atoms in an optical lattice. By the comparison of our experimental data with a spatially resolved, time-dependent bosonic Gutzwiller calculation, we obtain good quantitative agreement. This allows for a clear identification of the amplitude mode, showing that it can be detected with full momentum resolution by going beyond the linear response regime. A systematic shift of the sound and amplitude modes' resonance frequencies due to the finite Bragg beam intensity is observed.
authors.affiliation: Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität, 60438 Frankfurt/Main, Germany.
authors.forename: Ulf
authors.initials: U
authors.lastname: Bissbort
authors.forename: Sören
authors.initials: S
authors.lastname: Götze
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Li
authors.forename: Jannes
authors.initials: J
authors.lastname: Heinze
authors.forename: Jasper S
authors.initials: JS
authors.lastname: Krauser
authors.forename: Malte
authors.initials: M
authors.lastname: Weinberg
authors.forename: Christoph
authors.initials: C
authors.lastname: Becker
authors.forename: Klaus
authors.initials: K
authors.lastname: Sengstock
authors.forename: Walter
authors.initials: W
authors.lastname: Hofstetter