title: Spontaneous breaking of spatial and spin symmetry in spinor condensates.
abstract: Parametric amplification of quantum fluctuations constitutes a fundamental mechanism for spontaneous symmetry breaking. In our experiments, a spinor condensate acts as a parametric amplifier of spin modes, resulting in a twofold spontaneous breaking of spatial and spin symmetry in the amplified clouds. Our experiments permit a precise analysis of the amplification in specific spatial Bessel-like modes, allowing for the detailed understanding of the double symmetry breaking. On resonances that create vortex-antivortex superpositions, we show that the cylindrical spatial symmetry is spontaneously broken, but phase squeezing prevents spin-symmetry breaking. If, however, nondegenerate spin modes contribute to the amplification, quantum interferences lead to spin-dependent density profiles and hence spontaneously formed patterns in the longitudinal magnetization.
authors.affiliation: Institut für Quantenoptik, Leibniz Universität Hannover, 30167 Hannover, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Scherer
authors.forename: B
authors.initials: B
authors.lastname: Lücke
authors.forename: G
authors.initials: G
authors.lastname: Gebreyesus
authors.forename: O
authors.initials: O
authors.lastname: Topic
authors.forename: F
authors.initials: F
authors.lastname: Deuretzbacher
authors.forename: W
authors.initials: W
authors.lastname: Ertmer
authors.forename: L
authors.initials: L
authors.lastname: Santos
authors.forename: J J
authors.initials: JJ
authors.lastname: Arlt
authors.forename: C
authors.initials: C
authors.lastname: Klempt