Effect of pinning sites on the decay of the orientational order of a vortex lattice

Abstract

Molecular dynamics method has been used to simulate dynamics of a vortex population in a micron size sample. The time development of the vortex system has been traced by plotting the time dependence of the standard deviation of the angular separation sigma(phi) of the nearest vortices. The oscillatory decaying behavior of sigma(phi) has been discovered while the vortex population settles to a stable equilibrium configuration after hopping around various relative equilibrium configurations. A single and a number of attractive pinning centers are included to study the extent of the pinning effect to this equilibrium process. Randomly scattered pinning sites have distorted this oscillatory behavior to the extent that they have been shielded more effectively at higher applied fields.