Roles of pinning strength and density in vortex melting

Abstract

We have investigated the role of pinning strength and density on the equilibriumvortex-lattice to vortex-liquid phase transition under several applied magnetic fields. Thisstudy was conducted using a series of molecular dynamic simulations on several sampleswith different strengths and densities of pinning sites which are arranged in periodic squarearrays. We have found a single solid–liquid vortex transition when the vortex filling factorn>1. We have found that, for fixed pinning densities and strengths, the melting temperature,Tm, decreases almost linearly with increasing magnetic field. Our results provide directnumerical evidence for the significant role of both the strength and density of pinningcenters on the position of the melting line. We have found that the vortex-lattice tovortex-liquid melting line shifts up as the pinning strength or the pinning density wasincreased. The effect on the melting line was found to be more pronounced at small valuesof strength and density of pinning sites.