Simulation of vortex creep in type-II superconductors

The experimental study pointed out that voltage noise power spectrum has two types. One is broad-band noise (BBN), which results from bulk pinning. The other is narrow-band noise (NBN), which is observed near critical current. Therefore, it is expected to occur in the region of vortex creep. NBN is sensitive to even direction of external current, which is supposed to result from surface condition of superconductors. To find out origin of NBN, we perform simulations of the vortex dynamics in the 2D system with pinning array. Simulations show that the periodic pinning potential generates NBN and the first peak frequency is proportional to voltage. We find that the initial vortex arrangement has effect on the first peak frequency.