Non-equilibrium supercurrent through mesoscopic ferromagnetic weak links

¹ Institut für Theoretische Festkörperphysik, Universität Karlsruhe D-76128 Karlsruhe, Germany
² Materials Physics Laboratory, Helsinki University of Technology FIN-02015 HUT, Finland
³ Quantum Transport Group, TU Delft - 2600 GA Delft, The Netherlands

Corresponding author: Tero.T.Heikkila@hut.fi

Received: 27 March 2000
Accepted: 14 June 2000

Abstract

We consider a mesoscopic normal metal, where the spin degeneracy is lifted by a ferromagnetic exchange field or Zeeman splitting, coupled to two superconducting reservoirs. As a function of the exchange field or the distance between the reservoirs, the supercurrent through this device oscillates with an exponentially decreasing envelope. This phenomenon is similar to the tuning of a supercurrent by a non-equilibrium quasiparticle distribution between two voltage-biased reservoirs. We propose a device combining the exchange field and non-equilibrium effects, which allows us to observe a range of novel phenomena. For instance, part of the field-suppressed supercurrent can be recovered by a voltage between the additional probes.