Decoupling and decommensuration in layered superconductors with columnar defects

TL;DR

This paper investigates how columnar defects influence the decoupling transition and pinning behavior in layered superconductors with flux lattices, revealing enhanced transition temperatures and a possible explanation for observed melting line anomalies.

Contribution

It introduces a theoretical analysis of the effects of columnar defects on decoupling and decommensuration transitions in layered superconductors, including the impact on transition temperatures and pinning.

Findings

Columnar defects increase the decoupling transition temperature by ~B^2.

Reentrant recoupling transition occurs at high disorder levels.

Decommensuration transition explains a kink in the melting line.

Abstract

We consider layered superconductors with a flux lattice perpendicular to the layers and random columnar defects parallel to the magnetic field B. We show that the decoupling transition temperature Td, at which the Josephson coupling vanishes, is enhanced by columnar defects by an amount ~B^2 relative to Td. Decoupling by increasing field can be followed by a reentrant recoupling transition for strong disorder. We also consider a commensurate component of the columnar density and show that its pinning potential is renormalized to zero above a critical long wavelength disorder. This decommnesuration transition may account for a recently observed kink in the melting line.