EXTREME CRITICAL-TEMPERATURE ENHANCEMENT OF AL BY TUNNELING IN NB/AOX/AL/ALOX/NB TUNNEL-JUNCTIONS

Current - voltage measurements on high conductance Nb/AIOx/Al/AlOx/Nb tunnel junction devices show a step in the sub-gap structure corresponding to the difference in the energy gaps V=2(ΔNb-ΔAl) of the two superconductors. The measured ΔAl is large and persists to temperature considerably in excess of the equilibrium critical temperature of the Al. This is interpreted as arising from a tunnel-induced gap enhancement which is an order of magnitude larger than has been seen previously. © 1990, Elsevier Science Publishers B.V. (North-Holland). All rights reserved.