Abstract
Using a detwinned YBa 2Cu 3O 7 monocrystal and acoustic-resonance spectroscopy, we measured internal friction Q −1 = Δ f/ f r through the 91-K superconducting-transition temperature. We show measurements for the first ten macroscopic resonance frequencies f r. None of the modes show classic BCS-model behavior based on simple-pairing, isotropic- s-electron, weak-coupling assumptions. Beside being non-BCS-like, essentially every mode behaves differently, suggesting a strongly anisotropic energy gap Δ( k), and practically ruling out any simple Fermi-surface gap function, especially s-wave. Some modes actually show increasing Q −1 upon cooling below T c , suggesting either strong Fermi-surface changes or lattice-relaxation mechanisms.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
