title: Transport spectroscopy on trapped superconducting nano-islands of Pb: signature of unconventional pairing.
abstract: Elemental bulk lead (Pb) is a conventional type I, spin-singlet (s-wave) superconductor with a critical temperature T c = 7.2 K and a critical magnetic field H c = 800 Oe. However, it is known that at mesoscopic length scales, like in point-contact geometries, Pb shows significantly higher critical field, sometimes up to several Tesla. We have used this property to trap a small superconducting nano-droplet of Pb by forming a metallic point contact on Pb and then applying a magnetic field larger than 800 Oe that drives the bulk of the material non-superconducting. From systematic magnetic field dependent behaviour of the point-contact spectra measured across such a trapped island of Pb we show that the superconducting order parameter of mesoscopic Pb mixes non-trivially with magnetic field possibly due to the emergence of a local spin-triplet component at such length scales. From comparative studies with Nb-based point contacts we surmise that the strong spin-orbit coupling in Pb leads to the emergence of the unconventional component in the order parameter of mesoscopic Pb.
authors.affiliation: Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, S. A. S. Nagar, Manauli, PO 140306, India.
authors.forename: Anshu
authors.initials: A
authors.lastname: Sirohi
authors.forename: Preetha
authors.initials: P
authors.lastname: Saha
authors.forename: Sirshendu
authors.initials: S
authors.lastname: Gayen
authors.forename: Avtar
authors.initials: A
authors.lastname: Singh
authors.forename: Goutam
authors.initials: G
authors.lastname: Sheet