Tunneling of quasiparticles in the normal-insulator-superconductor-insulator-normal geometry

The probability of quasiparticle transmission going through a normal-insulator- superconductor-insulator-normal (NISIN) geometry is theoretically calculated using Bogoliubov–de Gennes equations to investigate the feasibility of electron devices utilizing this geometry. This new calculation is able to include a current carried by Cooper pairs by employing hole injections from the outlet which destroy Cooper pairs at the outlet super- conductor-insulator boundary. Resonant tunneling phenomena occur even if the electron kinetic energy is less than the superconducting energy gap and electron tunneling probabilities are greatly modified by the resonance. When the unevenness of the superconductor (S) width thickness is large compared with the electron wavelength in the S layer, the resonance is smeared out in averaged tunneling probabilities. Then the tunneling probabilities can be controlled by the electron kinetic energy. Applications of the NISIN geometry for superconducting transistors are also discussed.