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Published Online February 21, 2008
Science DOI: 10.1126/science.1154115

Reports

Submitted on December 13, 2007
Accepted on February 1, 2008

Energy Gaps and Kohn Anomalies in Elemental Superconductors

P. Aynajian 1, T. Keller 2, L. Boeri 1, S. M. Shapiro 3, K. Habicht 4, B. Keimer 1*

1 Max-Planck-Institute for Solid State Research, Heisenbergstr. 1, D-70569 Stuttgart, Germany.
2 Max-Planck-Institute for Solid State Research, Heisenbergstr. 1, D-70569 Stuttgart, Germany. ; ZWE FRM-II, Technical University of Munich, Lichtenbergstr. 1, D-85748 Garching, Germany.
3 Brookhaven National Laboratory, Upton, New York 11973-5000, USA.
4 Hahn-Meitner-Institute, Glienicker Str. 100, D-14109 Berlin, Germany.

* To whom correspondence should be addressed.
B. Keimer , E-mail: b.keimer{at}fkf.mpg.de

The momentum and temperature dependence of the lifetimes of acoustic phonons in the elemental superconductors Pb and Nb was determined by resonant spin-echo spectroscopy with neutrons. In both elements, the superconducting energy gap extracted from these measurements was found to converge with sharp anomalies originating from Fermi-surface nesting (Kohn anomalies) at low temperatures. The results indicate electron many-body correlations beyond the standard theoretical framework for conventional superconductivity. A possible mechanism is the interplay between superconductivity and spin- or charge-density-wave fluctuations, which may induce dynamical nesting of the Fermi surface.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)