PHYSICA Angle-resolved photoemission study of Sr2RuO4; An extended van-Hove singularity in non-cuprate superconductor

We have performed high-resolution angle-resolved photoemission spectroscopy of a non-cuprate layered superconductor Sr2RuO 4 to study the electronic structure near the Fermi level (EF). The result shows an extended van Hove singularity (vHs) along the Ru-O bonding direction just like the cuprate, regardless of the character of the electronic states at EF. This suggests that the extended vHs is a general electronic structure of a two dimensional correlated d-electron metal. We also have found that the observed Fermi surface topology (one electron-like Fermi surface sheet centered at 1 " point and two hole-like ones centered at X point) is qualitatively different from the calculated Fermi surface topology (two electron-like Fermi sheets centered at F point and one hole-like one centered at X point) in the consequence of the existence of the vHs. 1