title: Nonspreading wave packets in three dimensions formed by an ultracold bose gas in an optical lattice.
abstract: We predict that an ultracold Bose gas in an optical lattice can give rise to a new form of condensation, namely, nonspreading 3D wave packets that reflect the symmetry of the Laplacian with a negative effective mass along the lattice direction and are allowed to exist in the absence of any trapping potential even in the limit of noninteracting atoms. This result also has strong implications for optical propagation in periodic structures.
authors.affiliation: National Institute for the Physics of Matter, INFM, Università Roma Tre, Via della Vasca Navale 84, 00146 Rome, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Conti
authors.forename: Stefano
authors.initials: S
authors.lastname: Trillo