title: Zero-energy states in rotating trapped Bose-Einstein condensates.
abstract: We have calculated low-lying quasiparticle excitation spectra of rotating three-dimensional Bose-Einstein condensates. We find, as opposed to the prediction of hydrodynamic continuum theories, a minimum in the Tkachenko mode spectrum at intermediate rotation frequencies of the harmonic trap. Such a minimum can harbour a Tkachenko quasiparticle with zero excitation energy. We discuss the experimental signatures of such a zero mode.
authors.affiliation: School of Physics, Monash University, Victoria 3800, Australia. tapio.simula@monash.edu
authors.forename: Tapio
authors.initials: T
authors.lastname: Simula