title: Unbinding of giant vortices in states of competing order.
abstract: We consider a two-dimensional system with two order parameters, one with O(2) symmetry and one with O(M), near a point in parameter space where they couple to become a single O(2+M) order. While the O(2) sector supports vortex excitations, these vortices must somehow disappear as the high symmetry point is approached. We develop a variational argument which shows that the size of the vortex cores diverges as 1/√Δ and the Berezinskii-Kosterlitz-Thouless transition temperature of the O(2) order vanishes as 1/ln(1/Δ), where Δ denotes the distance from the high-symmetry point. Our physical picture is confirmed by a renormalization group analysis which gives further logarithmic corrections, and demonstrates full symmetry restoration within the cores.
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom.
authors.forename: J M
authors.initials: JM
authors.lastname: Fellows
authors.forename: S T
authors.initials: ST
authors.lastname: Carr
authors.forename: C A
authors.initials: CA
authors.lastname: Hooley
authors.forename: J
authors.initials: J
authors.lastname: Schmalian