Critical Behavior of Layered Superconducting Films in Parallel Magnetic Field

TL;DR

This paper investigates the critical behavior of layered superconducting films under parallel magnetic fields, revealing anomalous magnetization tails and collective pinning effects near the decoupling transition.

Contribution

It introduces a fermion analogy to compute magnetization and uncovers novel fluctuation effects and pinning phenomena in layered superconductors.

Findings

Parallel magnetization exhibits an $H_{\parallel}^{-1}$ tail at high fields.

Entropic fluctuations influence vortex lattice behavior.

Collective pinning occurs due to planar defects aligned with the magnetic field.

Abstract

The equilibrium magnetization for layered superconducting films that experience a nonzero component, $H_{\parallel}$, of magnetic field applied parallel to the layers is computed at temperatures and at perpendicular field components in the vicinity of the decoupling transition. A fermion analogy is exploited for this purpose, whereby it is found that the parallel magnetization shows an anomalous $H_{\parallel}^{-1}$ tail at high fields due to entropic fluctuations of the (parallel) lattice of Josephson vortices. A collective pinning effect is also identified for $c$-axis transport limited by a single planar defect oriented parallel to both $c$ and to the applied magnetic field.