NUMERICAL-SIMULATION OF FLUX-PINNING DYNAMICS FOR A DEFECT IN A TYPE-II SUPERCONDUCTOR

We perform a computer simulation of the flux-pinning dynamics for a si ngle defect under the presence of both the applied current and the ext ernal magnetic field by directly solving the time-dependent Ginzburg-L andau equation coupled with the Maxwell equation in a two-dimensional rectangular region. With one vortex flow path and a single defect, we found two types of vortex motions around the defect, which are one-flu x and two-flux pinning, depending on the size of the defect. The crite rion of the two-flux pinning is studied by both numerical simulation a nd a simplified free-energy calculation. We also present the effect of a single defect on the V-I characteristics.