A superconducting transistor based on quasiparticle trapping

Abstract

We propose a new superconducting electronic device which can provide either current or voltage amplification of low-level electrical signals at low temperatures. The device, which we call the quatratran, is based on quasiparticle trapping from a superconductor into a normal metal, coupled with normal-insulator-superconductor (NIS) tunnel junctions. Quasiparticles injected into the S electrode of a first junction are trapped in an N layer, producing excited charge carriers. This N layer is also used as the N electrode of a second NIS junction which produces an amplified signal. We explain the principles of operation and describe the electronic characteristics. Results from test devices demonstrate the soundness of the principles. We also suggest how quatratrans can be applied to the detection of particles and radiation.