Optical response in the mixed state of Tl2Ba2CaCu2O8 epitaxial films

Measurements of resistive photoresponse (PR) excited with a mechanically chopped beam of He-Ne laser in epitaxial thin films of Tl2Ba2CaCu2O8 (T1-2212) superconductor are reported. Our objective was to study the existence of photo-enhanced flux creep (PFC), which has been suggested as one of the mechanisms for PR in YBa2Cu3O7 films. Such effects are expected to be enhanced in T1-2212 because of the low activation barrier for flux motion in this highly anisotropic superconductor. Our measurements, carried out with a sensitivity of similar to 0.5 mu V, however, do not suggest PFC as the mechanism for PR. The data collected for different bias currents, magnetic field strength and chopping frequencies are in excellent agreement with a bolometric model for the PR. (C) 2000 Elsevier Science B.V. All rights reserved.