Abstract
Photovoltaic effects of Bi-2223/Ag and Bi-2212/Ag heterostructures under magnetic fields up to ± 9 T induced by continuous purple-laser irradiation have been investigated in a wide temperature range between 10 K and 350 K. There is a broad peak in the temperature dependence of Voc for the Bi-2223/Ag system near 45 K which can be ascribed to the minority phase of Bi-2212 within the Bi-2223 sample. The anomalous magnetic field dependence of Voc below 60 K suggests that the low temperature magnetic behavior of Voc for the Bi-2223/Ag system is greatly affected by the minority phase Bi-2212. No polarity reversal of Voc was observed at the superconducting transition of Bi-2212/Ag heterostructure, consisting with that for SmO0.7F0.3FeAs/Ag system but opposite to that of Bi-2223/Ag and YBCO/Ag systems. This observation indicates that the majority charge carriers in this heavily over-doped Bi-2212 are electrons other than holes. Our results show that the photo-induced voltage has a photovoltaic nature closely related to the built-in electric field of the intrinsic metal/superconductor interface. The magnitude and the direction of the built-in electric field can be changed by applying an external magnetic field and/or varying the laser intensity. Our data provide a new dimension of information for depicting a more comprehensive picture of metal/HTSC heterostructure system and may lead to new applications of high temperature superconductor in the field of photo-electronic and magnetic sensing devices.
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