Dynamics of Topological Defects in Type-II Superconductors under Gradients of Temperature/Spin Density

TL;DR

This paper models the movement of topological defects like domain walls and vortices in type-II superconductors driven by temperature or spin density gradients, combining numerical and analytical methods.

Contribution

It introduces a coupled Ginzburg-Landau and diffusion model that accounts for inhomogeneities in temperature and spin density affecting defect dynamics.

Findings

Domain walls move toward higher temperature/spin density regions.

Derived an analytical expression for vortex velocity.

Identified forces influencing defect motion, including thermal and spin accumulation forces.

Abstract

We theoretically investigate the motion of a domain wall and a vortex in type-II superconductors driven by inhomogeneities of temperature or spin density. The model consists of the time-dependent Ginzburg-Landau equation and the thermal/spin diffusion equation, whose transport coefficients (the thermal/spin conductivity and the spin relaxation time) depend on the order parameter, interpolating between values in the superconducting and normal states. Numerical and analytical calculations indicate that the domain wall moves toward the higher-temperature/spin-density region, where the order parameter is suppressed. We also derive an analytical expression for the vortex velocity. We can understand the dynamics of topological defects as processes that reduce the loss of condensation energy. We also analyze the driving force, the viscous force, the thermal force, and the force due to the spin accumulation gradient, on the basis of the momentum balance relations.