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Phys. Rev. Lett. 85, 5198–5201 (2000)

Evidence for Large Gap Anisotropy in Superconducting Pb from Phonon Imaging

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J. D. Short and J. P. Wolfe
Physics Department and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801

Received 10 April 2000; published in the issue dated 11 December 2000

We report the first ballistic phonon images of superconducting Pb. Unusual absorption lines are observed for phonon wave vectors in {111} planes. We show that a highly anisotropic energy gap can lead to sharply defined directions of phonon attenuation. Overhauser and Daemen [Phys. Rev. Lett. 61, 1885 (1988)] postulated a spin-density-wave ground state for Pb that leads to directions of strongly reduced gap. By applying their idea to the actual Fermi surface of Pb, we predict phonon attenuation directions consistent with the data.

© 2000 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.85.5198
DOI:
10.1103/PhysRevLett.85.5198
PACS:
74.25.Ld, 74.25.Jb, 74.25.Kc, 75.30.Fv