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; Wolf-Dieter Schneider

doi:10.1103/PhysRevLett.102.207002

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, Wolf-Dieter Schneider

DOI 10.1103/PhysRevLett.102.207002 · Physical Review Letters

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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.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Pb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.2	Pressure unresolved	unknown
Pb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Pb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown