Aynajian, P. ; Keller, T. ; Boeri, L. ; Shapiro, S.M. ; Habicht, K. ; Keimer, B.: Energy gaps and Kohn anomalies in elemental superconductors. Science 319 (2008), p. 1509-1512
10.1126/science.1154115
Abstract:
The momentum and temperature dependence of the lifetimes of acoustic phonons in the elemental superconductors lead and niobium were 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.