Pinning of Flux Lines by Planar Defects

TL;DR

This paper investigates how planar defects affect flux line behavior in type-II superconductors, revealing a new planar glass phase with unique elastic and transport properties, and showing the instability of the Bragg glass phase due to these defects.

Contribution

It introduces the concept of a planar glass phase caused by planar defects and analyzes its properties, extending understanding of vortex matter in disordered superconductors.

Findings

Planar defects destabilize the Bragg glass phase.

A new planar glass phase with diverging shear and tilt moduli is identified.

Flux creep exhibits nonlinear resistivity with an exponential dependence.

Abstract

The influence of randomly distributed point impurities and planar defects on order and transport in type-II superconductors and related systems is studied. It is shown that the Bragg glass phase is unstable with respect to planar efects. Even a single weak defect plane oriented parallel to the magnetic field as well as to one of the main axis of the Abrikosov flux line lattice is a relevant perturbation in the Bragg glass. A defect that is aligned with the magnetic field restores the flux density oscillations which decay algebraically with the distance from the defect. The theory exhibits striking similarities to the physics of a Luttinger liquid with a frozen impurity. The exponent for the flux line creep in the direction perpendicular to a relevant defect is derived. We find that the flux line lattice exhibits in the presence of many randomly distributed parallel planar defects aligned to the magnetic field a new glassy phase which we call planar glass. The planar glass is characterized by diverging shear and tilt moduli, a transverse Meissner effect, resistance against shear deformations. We also obtain sample to sample fluctuations of the longitudinal magnetic susceptibility and an exponential decay of translational long range order in the direction perpendicular to the defects. The flux creep perpendicular to the defects leads to a nonlinear resistivity $\rho(J \to 0)\sim \exp[-(J_D/J)^{3/2}]$. Strong planar defects enforce arrays of dislocations that are located at the defects with a Burgers vector parallel to the defects in order to relax shear strain.