Frequency response of AC susceptibility in high temperature superconductors

Based on the thermal activation, considering the two most important energies, namely thermal activation energy, which drives the system to a more disordered state, and effective pinning energy, which keeps the system in order, a general description of the temperature dependence of resistivity under magnetic fields for high temperature superconductors has been deduced. The temperature dependence of resistivity can be expressed as ρ=ρn(1−x)s, with the energy ratio x=Ueff(T,B,J)/kBT. This extended thermally activated model is a consistent description of the vortex glass theory. Our model is applied to the frequency response of AC susceptibility in YBCO superconductors; the results are in good agreement with the proposed model.