On the macroscopic and microscopic origin of the photovoltaic effect in YBCO thin films

Abstract The study of a photovoltaic component of the net voltage arising in illuminated YBCO thin films with different morphology was carried out. The anisotropy of the photovoltages in the film plane correlates with the anisotropy of such physical characteristics of the samples as resistivity and microwave absorption and implies the existence of a macroscopic preferential direction even in the film deposited on an isotropic MgO substrate. Disappearance of the photovoltaic signal below T c in the films exhibiting an appreciable residual resistivity is an unambiguous indication of its relation with extended defects inside the superconducting YBCO phase. A model for the microscopic asymmetry of the flow of the photocurrent generated at the boundaries of an isolated defect was proposed, and the contributions coming from some types of extended structural defects into the effect were estimated.