title: Ge/Si nanowire mesoscopic Josephson junctions.
abstract: The controlled growth of nanowires (NWs) with dimensions comparable to the Fermi wavelengths of the charge carriers allows fundamental investigations of quantum confinement phenomena. Here, we present studies of proximity-induced superconductivity in undoped Ge/Si core/shell NW heterostructures contacted by superconducting leads. By using a top gate electrode to modulate the carrier density in the NW, the critical supercurrent can be tuned from zero to greater than 100 nA. Furthermore, discrete sub-bands form in the NW due to confinement in the radial direction, which results in stepwise increases in the critical current as a function of gate voltage. Transport measurements on these superconductor-NW-superconductor devices reveal high-order (n = 25) resonant multiple Andreev reflections, indicating that the NW channel is smooth and the charge transport is highly coherent. The ability to create and control coherent superconducting ordered states in semiconductor-superconductor hybrid nanostructures allows for new opportunities in the study of fundamental low-dimensional superconductivity.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Xiang
authors.forename: A
authors.initials: A
authors.lastname: Vidan
authors.forename: M
authors.initials: M
authors.lastname: Tinkham
authors.forename: R M
authors.initials: RM
authors.lastname: Westervelt
authors.forename: Charles M
authors.initials: CM
authors.lastname: Lieber
mesh_terms: D004553:Electric Conductivity; D004559:Electric Wiring / Q000295:instrumentation*; D004867:Equipment Design; D005857:Germanium / Q000737:chemistry*; D036103:Nanotechnology / Q000295:instrumentation*; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure*; D012666:Semiconductors; D012825:Silicon / Q000737:chemistry*
chemical_list: D005857:Germanium; D012825:Silicon