EXPERIMENTAL AND THEORETICAL INVESTIGATION OF PHOTOINDUCED THERMOELECTRIC EFFECT IN HIGH-TEMPERATURE SUPERCONDUCTORS

Thermopower of YBa2Cu3O6.9 superconducting film was investigated using the modulation technique. A geometry (the specimen had a bridge-like structure with a length 4mm and a width 0.15mm) and an investigation scheme were used which provided to initiate on the same sample characteristic conditions of the wellknown experiments: their results, concerning the giant peak in thermopower, previously were seemed contradictive [1-9]. The analysis of our data gave grounds to conclude that the giant peak, which in certain conditions also reveals itself in our measurements, is caused by nonequilibrium effects [10] rather than by fluctuations [11]. Under the conditions of laser irradiation the differential thermopower acquires an additional term. Its physical origin lies in the branch imbalance, created in superconductors by the electromagnetic field [12].