Microwave-induced dc voltages in a YBa2Cu3O7-δ single crystal

Microwave-induced dc voltages in a YBa2Cu3O7-δ single crystal have been observed along its c axis with or without a dc bias current by utilizing standing waves near the end of an X-band (8 endash 12 GHz) waveguide. With a dc bias current present, the induced voltages arise from both bolometric and nonbolometric effects; however, the characteristics of the induced voltages versus bias currents due to these two effects are distinctively different. In the bolometric effect, the induced voltages are simply due to a resistive change caused by microwave heating whereas the induced voltages from the nonbolometric effect are due to the Josephson vortex flow generated by the microwave H field below the superconducting transition temperature. Without a dc bias current, the induced voltages are attributed to the inverse ac Josephson effect which requires the presence of both the microwave E and H fields. copyright 1996 The American Physical Society