We characterize the nature of the Van Hove singularity near the Fermi energy () in Y using ultrahigh energy resolution (10 meV) angle-resolved photoemission spectroscopy, together with corresponding first-principles spectra intensity computations. The singularity, related to Cu planes, is located about 19 meV below at the point in the Brillouin zone and arises from a band which is nearly dispersionless along the to direction. Such an "extended" saddle point would render the band structure quasi-1D and yield a power law divergence in the density of states, allowing the occurrence of of order 100 K even in a weak coupling BCS scheme.
- Received 4 March 1994
- Published in the issue dated 12 December 1994
© 1994 The American Physical Society