Vortex dynamics in the mixed state of a type-II superconductor
Abstract
The mixed state of extreme type II superconductors is studied order to determine how an applied transport current interacts with vortices. The Ginzburg-Landau theory is applied first to determine the force balance equation on stationary vortices in the mixed state. Motivated by experimental data on the recently discovered Hall angle anomaly in the mixed state, we also investigate the flux flow state in which vortices move with a constant velocity. The two fundamental models for the flux flow state, one suggested by Bardeen and Stephen and the other by Nozieres and Vinen, are studied with a focus on the force balance equation and the paramagnetic current at the vortex core. To further study the paramagnetic current generated in a moving vortex core, we resort to the microscopic Bogoliubov-de Gennes equations. By making use of the solution obtained by Caroli et al for a stationary vortex, we solve the Bogoliubov-de Gennes equations for a vortex in the flux flow state via a perturbative method. The paramagnetic current at a moving vortex core is determined using this solution. We find that the paramagnetic current and the related dissipation at the vortex core result from a number of concomitant effects. The characteristics of the paramagnetic current due to each effect is determined. From these results, we then obtain microscopically a force balance equation for an isolated moving vortex. Using this force balance equation, we discuss how the Hall angle anomaly can be explained.
Degree
Ph.D.
Advisors
Giuliani, Purdue University.
Subject Area
Condensation
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