title: Condensing Magnons in a Degenerate Ferromagnetic Spinor Bose Gas.
abstract: We observe the quasicondensation of magnon excitations within an F=1 ^{87}Rb spinor Bose-Einstein condensed gas. Magnons are pumped into a ferromagnetically ordered gas, allowed to equilibrate to a nondegenerate distribution, and then cooled evaporatively at near-constant net longitudinal magnetization, whereupon they condense. The critical magnon number, spatial distribution, and momentum distribution indicate that magnons condense in a potential that is uniform within the volume of the ferromagnetic condensate. The macroscopic transverse magnetization produced by the degenerate magnon gas remains inhomogeneous within the ∼10  s equilibration time accessed in our experiment, and includes signatures of Mermin-Ho spin textures that appear as phase singularities in the magnon quasicondensate wave function.
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: Fang
authors.initials: F
authors.lastname: Fang
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Olf
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: Shun
authors.initials: S
authors.lastname: Wu
authors.affiliation: 5. Physikalisches Institut, Universität Stuttgart, 70550 Stuttgart, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Kadau
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.|Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Dan M
authors.initials: DM
authors.lastname: Stamper-Kurn