Effect of the exchange interaction on the Josephson current and the energy spectrum of a superconducting junction with a paramagnetic tunnel barrier

Abstract

Within the framework of a microscopic theory, we show that paramagnetic moments contained in a dielectric layer between two superconductors induce destruction of Cooper pairs in the processes of tunneling and reflection from the interfaces with a spin flip. As a consequence, the dc Josephson critical current reduced, and quasiparticle excitations of a new type with energies less than the superconducting gap appear. These excitations are characterized by strong damping due to scattering which arises from the breaking of translational invariance in the plane of the interface. The results of this study can be used to interpret tunneling experiments on a Pb/Er(OH)3/Pb structure