Persistent supercurrents in ring-shaped Bi_2Sr_2CaCu_2O_x single crystal

摘要

A superconducting ring could be used to simulate the supercurrent conduction, and its interaction with magnetic vortices in a superconducting solenoid, allowing one to investigate the nature of the vortex structure and its pinning in the presence of the persistent supercurrent. The dissipation of the persistent supercurrent has been studied in a ring-shaped high purity single crystal of Bi_2Sr_2CaCu_2O_x in order to obtain the information about the exponent μ, a parameter in the scaling relation between the effective energy barrier against vortex motion U_(eff) and the persistent current density J. The measurements of the persistent supercurrent decay show a transition from a strongly nonlogarithmic to a logarithmic decay regime with an increasing temperature. In response to a small increase in the concentration of oxygen vacancies μ decreases in the logarithmic decay regime but remains almost constant in the nonlogarithmic one.