title: Epitaxy of semiconductor-superconductor nanowires.
abstract: Controlling the properties of semiconductor/metal interfaces is a powerful method for designing functionality and improving the performance of electrical devices. Recently semiconductor/superconductor hybrids have appeared as an important example where the atomic scale uniformity of the interface plays a key role in determining the quality of the induced superconducting gap. Here we present epitaxial growth of semiconductor-metal core-shell nanowires by molecular beam epitaxy, a method that provides a conceptually new route to controlled electrical contacting of nanostructures and the design of devices for specialized applications such as topological and gate-controlled superconducting electronics. Our materials of choice, InAs/Al grown with epitaxially matched single-plane interfaces, and alternative semiconductor/metal combinations allowing epitaxial interface matching in nanowires are discussed. We formulate the grain growth kinetics of the metal phase in general terms of continuum parameters and bicrystal symmetries. The method realizes the ultimate limit of uniform interfaces and seems to solve the soft-gap problem in superconducting hybrid structures.
authors.affiliation: Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark.
authors.forename: P
authors.initials: P
authors.lastname: Krogstrup
authors.affiliation: Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark.
authors.forename: N L B
authors.initials: NL
authors.lastname: Ziino
authors.affiliation: Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark.
authors.forename: W
authors.initials: W
authors.lastname: Chang
authors.affiliation: Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark.
authors.forename: S M
authors.initials: SM
authors.lastname: Albrecht
authors.affiliation: Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark.
authors.forename: M H
authors.initials: MH
authors.lastname: Madsen
authors.affiliation: 1] Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark [2] Department of Wind Energy, Technical University of Denmark, Risø Campus, 4000 Roskilde, Denmark.
authors.forename: E
authors.initials: E
authors.lastname: Johnson
authors.affiliation: 1] Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark [2] Nano-Science Center, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Nygård
authors.affiliation: Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark.
authors.forename: C M
authors.initials: CM
authors.lastname: Marcus
authors.affiliation: Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark.
authors.forename: T S
authors.initials: TS
authors.lastname: Jespersen