Condensed Matter Seminar: Two Dimensional Exfoliated Superconductor Devices

Exfoliated materials offer a new approach to the study of superconductivity at the two-dimensional limit. In my talk I will review our work on the layered superconductor NbSe2, where superconductivity can be retained down to the few layer limit. NbSe2 is an Ising superconductor, where a strong spin-orbit effect locks the spins at out-of-plane directions, and superconductivity can be retained up to high in-plane fields. I will describe our tunneling experiments, measured using van der Waals (vdW) barriers, where we track the spectra down to the 2D limit at high magnetic field. I will then describe a novel type of planar Josephson device, consisting entirely of vdW materials, where superconductivity is induced into graphene using ultrathin NbSe2 as superconducting contacts. In these devices supercurrent is sustained up to the few Tesla limit, and is limited by the Zeeman response of the graphene electrodes. The data, showing a suppression and recovery of the supercurrent, is interpreted in terms of a Zeeman-driven 0-pi transition.