Reduction of the Superconducting Gap of Ultrathin Pb Islands Grown on Si(111)

Christophe Brun, I-Po Hong, François Patthey, I. Yu. Sklyadneva, R. Heid, P. M. Echenique, K. P. Bohnen, E. V. Chulkov, and Wolf-Dieter Schneider
Phys. Rev. Lett. 102, 207002 – Published 19 May 2009

Abstract

The energy gap Δ of superconducting Pb islands grown on Si(111) was probed in situ between 5 and 60 monolayers by low-temperature scanning tunneling spectroscopy. Δ was found to decrease from its bulk value as a function of inverse island thickness. Corresponding Tc values, estimated using bulk gap-to-Tc ratio, are in quantitative agreement with ex situ magnetic susceptibility measurements, however, in strong contrast to previous scanning probe results. Layer-dependent ab initio density functional calculations for freestanding Pb films show that the electron-phonon coupling constant, determining Tc, decreases with diminishing film thickness.

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  • Received 12 December 2008

DOI:https://doi.org/10.1103/PhysRevLett.102.207002

©2009 American Physical Society

Authors & Affiliations

Christophe Brun1, I-Po Hong1, François Patthey1, I. Yu. Sklyadneva2,3, R. Heid4, P. M. Echenique2,5, K. P. Bohnen4, E. V. Chulkov2,5, and Wolf-Dieter Schneider1

  • 1École Polytechnique Fédérale de Lausanne (EPFL), Institut de Physique de la Matière Condensée, CH-1015 Lausanne, Switzerland
  • 2Donostia International Physics Center (DIPC), Paseo de Manuel Lardizabal, 4, 20018 San Sebastián/Donostia, Basque Country, Spain
  • 3Institute of Strength Physics and Materials Science, Prospekt Academicheski 2/1, 634021, Tomsk, Russia
  • 4Forschungszentrum Karlsruhe, Institut für Festkörperphysik, P.O. Box 3640, D-76021, Karlsruhe, Germany
  • 5Departamento de Física de Materiales and Centro Mixto CSIC-UPV/EHU, Facultad de Ciencias Químicas, UPV/EHU, Apartado 1072, 20080 San Sebastián/Donostia, Basque Country, Spain

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Vol. 102, Iss. 20 — 22 May 2009

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