title: Competitive localization of vortex lines and interacting bosons.
abstract: We present a theory for the localization of three-dimensional vortex lines or two-dimensional bosons with a short-ranged repulsive interaction which are competing for a single columnar defect or potential well. For two vortices we use a necklace model approach to find a new kind of delocalization transition between two different states with a single bound particle. This exchange-delocalization transition is characterized by the onset of vortex exchange on the defect for sufficiently weak vortex-vortex repulsion or sufficiently weak binding energy corresponding to high temperature. We calculate the transition point and order of the exchange-delocalization transition. A generalization of this transition to an arbitrary vortex number is proposed.
authors.affiliation: Max-Planck-Institut für Kolloid- und Grenzflächenforschung, 14424 Potsdam, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Kierfeld
authors.forename: V M
authors.initials: VM
authors.lastname: Vinokur