The European physical journal. B: Condensed matter physics vol:26 issue:3 pages:291-296
date:Katholieke Univ Leuven, Lab Vaste Stoffys Magnetisme, B-3001 Louvain, Belgium; Univ Sofia, Fac Phys, Dept Theoret Phys, Sofia 1164, Bulgaria; Inst Sci Mat & Rayonnement, GREYC Instrumentat, F-14050 Caen, France
The generation of harmonics of the voltage response is considered when an AC current is applied through a superconducting film above T-c. It is shown that almost at all temperatures the mechanism of the temperature oscillations created by the AC current and the temperature dependence of the resistance dominates over the isothermal nonlinear electric conductivity. Only in a narrow critical region close to T-c the latter is essential for the generation of the harmonics. A detailed investigation of harmonics generation provides an accurate method for measuring the thermal boundary conductance between the film and the insulating substrate. The critical behaviour of the third harmonic will give a new method for the determination of the lifetime of metastable Cooper pairs above T-c. The comparison of the calculated fifth harmonics of the voltage with the experiment is proposed as an important test for the applicability of the employed theoretical models.