Topological defects in the random-field XY model and the pinned vortex lattice to vortex glass transition in type-II superconductors.

TLDR: The connection between the possible existence of this phase transition in the random-field {ital XY} model and the magnetic-field-driven transition from a pinned vortex lattice to a vortex glass in weakly disordered type-II superconductors is discussed.

Abstract: As a simplified model of randomly pinned vortex lattices or charge-density waves, we study the random-field {ital XY} model on square ({ital d}=2) and simple cubic ({ital d}=3) lattices. We verify in Monte Carlo simulations that the average spacing between topological defects (vortices) diverges more strongly than the Imry-Ma pinning length as the random field strength {ital H} is reduced. We suggest that for {ital d}=3 the simulation data are consistent with a topological phase transition at a nonzero critical field {ital H}{sub {ital c}} to a pinned phase that is defect free at large length scales. We also discuss the connection between the possible existence of this phase transition in the random-field {ital XY} model and the magnetic-field-driven transition from a pinned vortex lattice to a vortex glass in weakly disordered type-II superconductors. {copyright} {ital 1996 The American Physical Society.}