A superconducting transistor with improved isolation between the input and output terminals

A new design for a multi-terminal superconducting transistor-like device exploiting tunnelling injection of quasiparticles is proposed, in which parasitic back-action of the acceptor junction (S₁IS₂) bias current on the injector junction (S₂FIS₃) current-voltage characteristic(CVC) is dramatically reduced as compared with that for the formerly reported quiteron (here S, I, and F denote a superconductor, an insulator and a ferromagnetic material). Improvement of the isolation is achieved owing to the short electron mean free path and short coherence length in a thin F layer that screens the superconducting energy gap in the perturbed S₂ layer preventing its manifestation in the CVC of the injector.