Fermi surface and extended van Hove singularity in the non-cuprate layered perovskite superconductor Sr2RuO4
Abstract
With high-resolution (≈22 me V) angle-resolved photoemission spectroscopy, the Fermi surface of the first copper free layered-perovskite superconductor, Sr2RuO4, was determined. We observed three bands to cross the Fermi energy in qualitative agreement with LDA band structure calculations; one electron-like surface encircling the Γ̄ point in the projected Brillouin zone, and two hole-like surfaces around the X̄ point. The most striking aspect of the measurements is the observation of an extended van Hove singularity. It is located 17 meV below the Fermi energy and extends around the M point for about 0.2 Å-1 along both the Γ̄ - M̄ - Γ̄ and the X̄ - M̄ - X̄ directions. These observations demonstrate that van Hove singularities near the Fermi surface are a more generic feature of layered oxides, and call for a clarification of their exact role in oxide superconductivity. © 1996 Plenum Publishing Corporation.