Superconducting device with transistor-like properties including large current amplification

Abstract

We have fabricated and studied a stacked superconducting double tunnel junction device with transistor-like properties. The intermediate electrode is a bilayer consisting of a Nb film together with an Al film that acts as a quasiparticle trap. Large current gains of more than 50 are observed at 4.2 K when the Al layer is normal. The operation is highly directional. Results are explained on the basis of trapping of quasiparticles from a superconductor into a normal metal, together with a conversion of relaxation energy into electronic excitations. Similar devices should have wide applications in low-temperature measurement and detection systems.

Non-Equilibrium in Josephson Junctions: Possible Transistor-Like Applications

“…In this very rough model the thermal conductance is much lower than the electron-phonon conductance which was assumed to be the limiting contribution in Ref. 4, and is probably limited by phonon trapping in the multilayer structure. Measurements on identical devices but with larger area junctions will better clear the underlying physical mechanisms.…”

“…The device investigated in this work consists of a superconducting electrode S 0 (Nb) which can inject quasiparticle excitations by tunneling into an intermediate Nb/Al bilayer electrode [4]. The Josephson curcent through this injector junction was suppressed by an external magnetic field oriented in the plane of the junction.…”

“…Details about the fabrication process and the layout of the device are discussed in Ref. 4. The two junctions were characterised by measuring the I-V curves.…”

Physics and applications of NIS junctions

“…Recently, a QTT operated at 4.2 K has produced values of differential current gain, dI out /dI in , as high as 80. [23]…”

Manipulative success and the unreal

“…The idea of a "quatratran" (Pepe et al, 2000), a transistor entirely based on exploiting the properties of quasi-particles, symbolizes the degree of manipulative success that physicists attribute to quasi-particles-even though they are well aware of the fact that all they really deal with are collective phenomena of electrons and crystal lattices.…”