Direct observation of the superconducting gap in phonon spectra

Abstract

We show that the superconducting energy gap $\hat{I}”$ can be directly observed in phonon spectra, as predicted by recent theories. In addition, since each phonon probes the gap on only a small part of the Fermi surface, the gap anisotropy can be studied in detail. Our neutron scattering investigation of the anisotropic conventional superconductor YNi${}_2$B${}_2$C demonstrates this new application of phonon spectroscopy.

4 pages, 5 figures