Fluctuation current in a superconducting ring caused by a thin solenoid
Department of Physics, Ritsumeikan University-BKC - Kusatsu City 525-8577, Japan
Received: 18 April 2015
Accepted: 22 July 2015
The fluctuating current due to the Cooper pair is calculated for a superconducting ring threaded by a thin magnetic solenoid that is arranged by time-varying flux. The formulation is based on the Fokker-Planck equation derived by the Langevin-type Landau-Ginzburg equation. The statistical average of the fluctuation current is calculated. As a special case, for the equilibrium state, the current shows a critical behavior near the transition point. In the presence of the time-varying flux, the current is calculated to be a highly nonlinear function of the electric field induced by the time variation of the flux, which yields a sort of the Ohmic law in the limit of the weak field.
PACS: 05.10.Gg – Stochastic analysis methods (Fokker-Planck, Langevin, etc.) / 05.40.-a – Fluctuation phenomena, random processes, noise, and Brownian motion / 74.25.N- – Response to electromagnetic fields
© EPLA, 2015