Optical response in the mixed state of Tl2Ba2CaCu2O8 epitaxial films

Measurements of resistive photoresponse (PR) excited with a mechanically ch opped 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 mec hanisms 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 h ighly anisotropic superconductor. Our measurements, carried out with a sens itivity of similar to 0.5 mu V, however, do not suggest PFC as the mechanis m for PR. The data collected for different bias currents, magnetic field st rength and chopping frequencies are in excellent agreement with a bolometri c model for the PR. (C) 2000 Elsevier Science B.V. All rights reserved.