Boson localization and correlated pinning of superconducting vortex arrays

Abstract

A theory of vortex pinning in high-temperature superconductors by correlated disorder in the form of twin boundaries, grain boundaries, and columnar defects is described. Mapping vortex trajectories onto boson world lines leads to a ``superfluid'' flux liquid at high temperatures, as well as low-temperature ``Bose-glass'' and ``Mott-insulator'' phases, in which the flux lines are localized. Currents perpendicular to the average vortex direction act like an electric field applied to charged bosons, while currents parallel to the field act like an imaginary magnetic field in this approach. We discuss the equilibrium and dynamic properties of these phases, and propose a scaling theory for the flux-liquid to Bose-glass transition, at which the linear resistivity vanishes. Although the Bose-glass predictions share some features with vortex-glass behavior predicted for point disorder, the response to tilting the magnetic field in the two cases differs dramatically, thus allowing the two theories to be distinguished experimentally.