title: Phase coherence of an atomic Mott insulator.
abstract: We investigate the phase coherence properties of ultracold Bose gases in optical lattices, with special emphasis on the Mott insulating phase. We show that phase coherence on short length scales persists even deep in the insulating phase, preserving a finite visibility of the interference pattern observed after free expansion. This behavior can be attributed to a coherent admixture of particle-hole pairs to the perfect Mott state for small but finite tunneling. In addition, small but reproducible kinks are seen in the visibility, in a broad range of atom numbers. We interpret them as signatures for density redistribution in the shell structure of the trapped Mott insulator.
authors.affiliation: Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Gerbier
authors.forename: Artur
authors.initials: A
authors.lastname: Widera
authors.forename: Simon
authors.initials: S
authors.lastname: Fölling
authors.forename: Olaf
authors.initials: O
authors.lastname: Mandel
authors.forename: Tatjana
authors.initials: T
authors.lastname: Gericke
authors.forename: Immanuel
authors.initials: I
authors.lastname: Bloch