Effect of dc electric field on the effective microwave surface impedance of YBa2Cu3O7/SrTiO3/YBa2Cu3O7 trilayers

Abstract

We have studied the effect of a dc electric field on the effective microwave surface impedance of a thin film YBa2Cu3O7/SrTiO3/YBa2Cu3O7 (YBCO/STO/YBCO) trilayer by a dielectric resonator technique. At large dc electric fields (≳105 V/cm), both the effective surface resistance and reactance of the sample decrease monotonically with increasing dc voltage applied to the to YBCO film, yielding at 25 K and 24.7 GHz ‖δRs/δVdc‖∼0.25 μΩ/V and ‖δXs/δVdc‖∼1.8 μΩ/V, respectively. A two-fluid analysis indicates that the changes in the surface impedance can be explained in terms of field induced changes in the superconducting carrier density of the top YBCO film.