Switchable Josephson junction based on interfacial exchange field

Abstract

We demonstrate exchange field switchable Josephson junctions where the Josephson tunneling between two superconducting layers (Nb and NbN) could be controlled by the relative magnetic alignment of two GdN ferromagnetic insulator layers sandwiching the Nb layer. The junction's working principle is based on the control of the superconducting state of one of the layers by means of the interfacial exchange field of the magnetic GdN layers. At zero field and low temperatures, the ground state of the junctions corresponds to an antiferromagnetic configuration of the two GdN layers that coexist with the superconducting state of the Nb layer. By applying an external field, the GdN layers are switched to a parallel configuration, thereby suppressing the superconductivity in Nb and hence the Josephson current via interfacial exchange. This switchable Josephson junction may be useful for integrated superconducting spintronics and quantum circuits.