Applied Physics Letters · 2008 · 58 citations · 18 references
Natural SciencesMaterials SciencePhysicsCondensed Matter PhysicsSolid State PhysicsSurface ScienceMagnetic Properties Of SolidsMagnetism In SolidsQuantum TunnelingSuperconducting MaterialsSurface MagnetismSurface PhysicsMagnetic ScatteringResonant CavitiesScatteringScattering SpectraScattering SpectroscopySuperconducting GapSuperconducting PropertiesSuperconducting Tunneling Spectroscopy
Tunneling spectroscopy was performed on Nb pieces prepared by the same processes used to etch and clean superconducting radio frequency (SRF) cavities. Air exposed, electropolished Nb exhibited a surface superconducting gap Δ=1.55meV, which is characteristic of a clean, bulk Nb. However, the tunneling density of states (DOS) was significantly broadened. The Nb pieces, which were treated with the same mild baking used to improve the Q slope in SRF cavities, reveal a sharper DOS. Good fits to the DOS were obtained by using the Shiba theory, suggesting that magnetic scattering of quasiparticles is the origin of the gapless surface superconductivity and a heretofore unrecognized contributor to the Q-slope problem of Nb SRF cavities.
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Quasiparticle and phonon lifetimes in superconductors
Steven B. Kaplan, C. C., D. N. Langenberg et al. · Physical review. B, Solid state · 1976 · 895 citations
Tunneling Study of Superconductivity near the Metal-Insulator Transition
R. C. Dynes, J. P. Garno, G. Hertel et al. · Physical Review Letters · 1984 · 432 citations