Atomic layer superconductivity. (8th May 2014)

• Record Type: Journal Article
• Authors: Stępniak, Agnieszka; Leon Vanegas, Augusto; Caminale, Michael; Oka, Hirofumi; Sander, Dirk; Kirschner, Jürgen; Yurimoto, Hisayoshi
• Is Part Of: Surface and interface analysis. Volume 46:Number 12/13(2014)
• Page Start: 1262
• Page End: 1267
• Publication Date: 2014-05-08
• Subjects: Surfaces (Physics) -- Periodicals; Surface chemistry -- Periodicals; Thin films -- Periodicals; 541.33
• DOI: 10.1002/sia.5516
• Languages: English
• ISSNs: 0142-2421

Abstract

<abstract abstract-type="main" id="sia5516-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p id="sia5516-para-0001">We present scanning tunneling microscopy (STM) studies of superconductivity of single layer Pb and Pb islands on Si(111). We perform temperature‐dependent measurements of the differential conductance from 0.38 to 4 K in fields of up to 6 T to extract the critical temperature <italic>T</italic><sub>C</sub> for the onset of superconductivity. We find <italic>T</italic><sub>C</sub> = 1.5 K for a single layer Pb on Si(111), and a critical out‐of‐plane field of 150 mT. This deviates from bulk Pb, where <italic>T</italic><sub>C</sub> = 7.2 K and <italic>H</italic><sub>C</sub> = 80 mT are reported. Our results provide the temperature dependence of the superconducting gap 2 Δ. A description of this dependence in the framework of the Bardeen–Cooper–Schrieffer theory indicates an energy gap of 2 Δ<sub>0</sub> = 0.7 meV, considerably less than the 2.7 meV found for bulk Pb. We observe that the insertion of a single layer Ag between Pb and Si suppresses superconductivity in the Pb film even at the lowest temperature of 0.38 K. Pb islands on Ag/Si(111) exhibit superconductivity. Our position‐dependent STM studies from a nine‐layer tall Pb island into the surrounding non‐superconducting Pb wetting layer on Ag/Si(111) reveal an extension of a superconducting gap in spectroscopy up to 20 nm away from the Pb island edge at 0.38 K. © 2014 The Authors Surface and Interface Analysis Published by John Wiley & Sons Ltd.</p> </abstract>