Polarization dependence of the tunnel current in superconductor-ferroelectric-superconductor junctions

In tunnel junctions with a ferroelectric barrier, a large resistance variation is observed upon ferroelectric switching, which can be induced by a short voltage pulse. Known as electroresistance, this phenomenon is connected to the interfacial screening of the electric field generated by the ferroelectric in the junction's electrodes. Usually realized in junctions with normal-metal electrodes, here we experimentally investigate these effects in junctions that combine the ferroelectric BiFeO₃ and different types of superconducting electrodes. Using piezoresponse force microscopy and electrical measurements, we find an unusual temperature dependence of the electroresistance, which reaches up to 10⁴%.The effects are discussed in terms of the interface charge-carrier depletion produced in the superconducting electrodes.