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Acoustic Evidence Against BCS Behavior in Monocrystal YBa2Cu307



M Lei, Albert Migliori, H M. Ledbetter


Using a detwinned YBa2Cu307 monocrystal and acoustic-resonance spectroscopy, we measured internal friction Q- = A If through the 91-K superconducting-transition temperature. We show measurements for the first ten macroscopic resonance frequencies fr 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 stronly anisotropic energy gap δ(k), andpractically ruling out any simple Fermi-surface gap function, especially s-wave.Some modes actually show increasing Q-1 upon cooling below Tc, suggesting either strong Fermi-surface changes or lattice-relation mechanisms.
Physica C-Superconductivity and Its Applications
C 282-287


acoustic, internal friction, monocrystal, superconductor, YBa<sub>2</sub>Cu<sub>3</sub>0<sub>7</sub>


Lei, M. , Migliori, A. and Ledbetter, H. (1999), Acoustic Evidence Against BCS Behavior in Monocrystal YBa<sub>2</sub>Cu<sub>3</sub>0<sub>7</sub>, Physica C-Superconductivity and Its Applications (Accessed October 2, 2023)
Created October 31, 1999, Updated October 12, 2021