title: Real-time observation of discrete Andreev tunneling events.
abstract: We provide a direct proof of two-electron Andreev transitions in a superconductor-normal-metal tunnel junction by detecting them in a real-time electron counting experiment. Our results are consistent with ballistic Andreev transport with an order of magnitude higher rate than expected for a uniform barrier, suggesting that only part of the interface is effectively contributing to the transport. These findings are quantitatively supported by our direct current measurements in single-electron transistors with similar tunnel barriers.
authors.affiliation: Low Temperature Laboratory, Aalto University, P.O. Box 13500, 00076 Aalto, Finland. ville.maisi@mikes.fi
authors.forename: V F
authors.initials: VF
authors.lastname: Maisi
authors.forename: O-P
authors.initials: OP
authors.lastname: Saira
authors.forename: Yu A
authors.initials: YA
authors.lastname: Pashkin
authors.forename: J S
authors.initials: JS
authors.lastname: Tsai
authors.forename: D V
authors.initials: DV
authors.lastname: Averin
authors.forename: J P
authors.initials: JP
authors.lastname: Pekola