Core states and spectral flow in vortex dynamics

I review the semi-classical picture of how states bound in the core of a vo rtex in an S-wave superconductor respond to relative motion between the vor tex and the condensate. I show how the momentum absorbed as a result of the Magnus force acting on the core leads to a change in the distribution of o ccupied states ("spectral flow"). In the simplest relaxation time approxima tion this modified distribution gives rise to the Kopnin-Kravtsov force on the vortex. (C) 2000 Elsevier Science B.V. All rights reserved.