Critical parameters and nonlinear dissipative properties of superconducting films in a strong high-frequency field
Abstract
We studied, both theoretically and experimentally, the dependence of the critical current in a superconducting film on the frequency and power of electromagnetic waves in the frequency range from 15 MHz to 104 MHz. The good agreement between the theoretical and experimental results enables us to determine the microscopic relaxation times of the order parameter τΔ and the quasiparticle distribution τϵ in the nonlinear regime where the amplitude of the variable current is comparable to the critical current. We find that the observed transition of the superconducting film into the resistive state is due to the dynamical Ginzburg–Landau depairing mechanism and not to either thermal or kinetic effects. We compute the nonlinear high-frequency dissipative conductivity of a superconducting film that has an anomaly in the neighborhood of the superconductor’s relaxation frequencies.