Electrostatic modulation of the superconducting transition in thin NdBa_2Cu_3O_(7-δ) films: the role of classical fluctuations

摘要

We have grown epitaxial Pb(Zr_(0.2)Ti_(0.8))O_3/NdBa_2Cu_3O_(7-δ)(PZT/NBCO) heterostructures and used the reversible ferroelectric polarization of Pb(Zr_(0.2)Ti_(0.8))O_3 to electrostatically modulate the superconducting transition of thin NdBa_2Cu_3O_(7-δ) films. For ～80 A thick NdBa_2Cu_3O_(7-δ) layers, reversing the ferroelectric polarization induces a 1 K change in the superconducting transition temperature. A Kosterlitz-Thouless (KT) analysis of the transitions has been used to extract the KT temperature T_(KT) for the two polarization states. From the values obtained, one can extract the change in the zero temperature superfluid density (n_s(0)). We find that the data imply a 6% change in n_s(0), a value consistent with the change in carrier density produced by the ferroelectric field effect.