title: Beliaev damping and Kelvin mode spectroscopy of a Bose-Einstein condensate in the presence of a vortex line.
abstract: It is demonstrated theoretically that the counter-rotating quadrupole mode in a vortex of Bose-Einstein condensates can decay into a pair of Kelvin modes via the Beliaev process. We calculate the spectral weight of a density-response function within the Bogoliubov framework, taking account of both Beliaev and Landau processes. Good agreement with experiment on 87 Rb by Bretin et al. [Phys. Rev. Lett., 100403 (2003)]] allows us to unambiguously identify the decayed mode as the Kelvin wave propagating along a vortex line.
authors.affiliation: Department of Physics, Okayama University, Okayama 700-8530, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Mizushima
authors.forename: M
authors.initials: M
authors.lastname: Ichioka
authors.forename: K
authors.initials: K
authors.lastname: Machida