2005/09/30 by Zhenyi Long, M. D. Stewart, M. D. Stewart Jr +2 · 1 citation
Physics and Astronomy · #BCS theory #Band gap #Condensed matter physics #Density of states #Electron #Fermi energy #Fermi level #Materials science #Pairing #Physics #Physics of Superconductivity and Magnetism #Quantum and electron transport phenomena #Quantum mechanics #Quantum tunnelling #Superconducting transition temperature #Superconductivity #Surface and Thin Film Phenomena #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.73.140507
10 pages, 4 figures
arxiv created 2006/03/30 · openalex publication_date 2006/04/28 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Tunneling measurements of the temperature dependence of the electronic density of states (DOS) of ultrathin bilayers of Pb and Ag reveal that their superconducting energy gap, \ensuremathΔ(T), evolves similarly to BCS predictions despite the presence of a large anomalous DOS at the Fermi energy that persists as T\ensuremath→0. The gap ratio, 2\ensuremathΔ(0)∕kBTc, systematically decreases more than 20% below the BCS universal value of 3.52 in bilayers with the lowest superconducting transition temperatures, Tc; a behavior we deem super-weakly coupled. A semiquantitative model suggests that the reduced gap ratios result from a systematic depletion of the DOS available for pairing that occurs with the growth of the anomalous DOS at the Fermi energy.