Vortex nucleation and annihilation in superconducting Corbino disks

The vortex dynamics in superconducting Corbino disks is studied both analytically and numerically. We found that, because the novel structure of Corbino disk serves a periodic circuit of moving vortices, the nucleation and annihilation processes of the vortices appreciably differ from those in ordinary four terminal geometry. Especially, the annihilation process is modified, since the Corbino system is a closed system for the vortices: the vortices are confined in the system until being pair-annihilated. It is shown that, when the transport current is increased above a critical value, the density of vortices significantly increases, because the annihilation process is suppressed by the vortex-vortex interaction effect. We point out that the fluctuations in the vortex density is large in this state.