Depairing current density in superconductors

The depairing current density in superconductors is theoretically investigated for magnetization and transport currents. It is found that the depairing current densities in both cases are higher than those predicted by Tinkham. One of the reasons for the higher current densities is that those are obtained at the transition point to the normal state, while Tinkham obtained in the superconducting state far from the transition boundary. Another reason is that the order parameter is larger than the equilibrium value, which contributes not only directly to a higher current density but also to a lower kinetic energy due to the current. (C) 2019 The Japan Society of Applied Physics