Atomic layer superconductivity

Agnieszka Stępniak, Augusto L. Vanegas, Michael Caminale, Hirofumi Oka, Dirk Sander, Jürgen Kirschner

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

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 TC for the onset of superconductivity. We find TC = 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 TC = 7.2 K and HC = 80 mT are reported. Our results provide the temperature dependence of the superconducting gap 2Δ. A description of this dependence in the framework of the Bardeen-Cooper-Schrieffer theory indicates an energy gap of 2Δ0= 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 nmaway fromthe Pb island edge at 0.38 K.

Original languageEnglish
Pages (from-to)1262-1267
Number of pages6
JournalSurface and Interface Analysis
Volume46
Issue number12-13
DOIs
Publication statusPublished - 2014 Dec 1

Keywords

  • Lead
  • Proximity effect
  • Scanning tunneling microscopy and spectroscopy
  • Silicon
  • Silver
  • Superconductivity

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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