Dynamics of 2D pancake vortices in layered superconductors

TL;DR

This paper investigates the dynamics of 2D pancake vortices in layered superconductors near the critical temperature, revealing how vortex motion, viscosity, and nonlinear effects depend on material properties, vortex orientation, and velocity.

Contribution

It introduces a new model for vortex dynamics in layered superconductors, accounting for the structure of vortex cores and their nonlinear behavior, deviating from traditional theories.

Findings

Viscous drag force depends on normal metal layer conductivity.

Vortex viscosity varies with the angle between magnetic field and layers.

Nonlinear effects emerge even at slow vortex velocities, with viscosity showing logarithmic dependence.

Abstract

The dynamics of 2D pancake vortices in Josephson-coupled superconducting/normal - metal multilayers is considered within the time-dependent Ginzburg-Landau theory. For temperatures close to $T_{c}$ a viscous drag force acting on a moving 2D vortex is shown to depend strongly on the conductivity of normal metal layers. For a tilted vortex line consisting of 2D vortices the equation of viscous motion in the presence of a transport current parallel to the layers is obtained. The specific structure of the vortex line core leads to a new dynamic behavior and to substantial deviations from the Bardeen-Stephen theory. The viscosity coefficient is found to depend essentially on the angle $\gamma$ between the magnetic field ${\bf B}$ and the ${\bf c}$ axis normal to the layers. For field orientations close to the layers the nonlinear effects in the vortex motion appear even for slowly moving vortex lines (when the in-plane transport current is much smaller than the Ginzburg-Landau critical current). In this nonlinear regime the viscosity coefficient depends logarithmically on the vortex velocity $V$.