title: Charge of a quasiparticle in a superconductor.
abstract: Nonlinear charge transport in superconductor-insulator-superconductor (SIS) Josephson junctions has a unique signature in the shuttled charge quantum between the two superconductors. In the zero-bias limit Cooper pairs, each with twice the electron charge, carry the Josephson current. An applied bias VSD leads to multiple Andreev reflections (MAR), which in the limit of weak tunneling probability should lead to integer multiples of the electron charge ne traversing the junction, with n integer larger than 2Δ/eVSD and Δ the superconducting order parameter. Exceptionally, just above the gap eVSD ≥ 2Δ, with Andreev reflections suppressed, one would expect the current to be carried by partitioned quasiparticles, each with energy-dependent charge, being a superposition of an electron and a hole. Using shot-noise measurements in an SIS junction induced in an InAs nanowire (with noise proportional to the partitioned charge), we first observed quantization of the partitioned charge q = e*/e = n, with n = 1-4, thus reaffirming the validity of our charge interpretation. Concentrating next on the bias region eVSD ~ 2Δ, we found a reproducible and clear dip in the extracted charge to q ~ 0.6, which, after excluding other possibilities, we attribute to the partitioned quasiparticle charge. Such dip is supported by numerical simulations of our SIS structure.
authors.affiliation: Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel;
authors.forename: Yuval
authors.initials: Y
authors.lastname: Ronen
authors.affiliation: Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel;
authors.forename: Yonatan
authors.initials: Y
authors.lastname: Cohen
authors.affiliation: Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel;
authors.forename: Jung-Hyun
authors.initials: JH
authors.lastname: Kang
authors.affiliation: Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel;
authors.forename: Arbel
authors.initials: A
authors.lastname: Haim
authors.affiliation: Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel; Dahlem Center for Complex Quantum Systems, Freie University, 14195 Berlin, Germany.
authors.forename: Maria-Theresa
authors.initials: MT
authors.lastname: Rieder
authors.affiliation: Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel; moty.heiblum@weizmann.ac.il.
authors.forename: Moty
authors.initials: M
authors.lastname: Heiblum
authors.affiliation: Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel;
authors.forename: Diana
authors.initials: D
authors.lastname: Mahalu
authors.affiliation: Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel;
authors.forename: Hadas
authors.initials: H
authors.lastname: Shtrikman
keywords: Andreev reflection; Josephson junction; quasiparticle charge; shot noise; superconductivity
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