Abstract
A system of superconducting layers with spacing d, in-layer penetration depth and Josephson coupling between neighboring layers J is studied. When J=0 the system exhibits a two-dimensional (2D) phase transition of vortex unbinding at a temperature . When ≲d a finite-size transition at > distinguishes this system from an XY model. When J≠0, but vortices are neglected, Josephson fluxon loops lead to a distinct phase transition at > in which a significant second nearest-layer coupling is generated. Competing vortices and fluxon loops lead to a three-dimensional phase transition at , where <<. For -based superconductors (≫d) is near if ≳J≫exp(-/), where is a renormalized vortex-core energy; drops to as J is decreased, accounting for data on / superlattices.
- Received 30 July 1992
DOI:https://doi.org/10.1103/PhysRevB.47.5947
©1993 American Physical Society