Extended Van Hove singularity in a noncuprate layered superconductor Sr2RuO4.

TLDR: Angle-resolved photoemission spectroscopy was performed on a ruthenate superconductor Sr{sub 2}RuO{sub 4} which shows an {ital extended} Van Hove singularity (VHS) at 20{plus_minus}2 meV below {ital E}{sub {ital F}} just like the cuprates, regardless of the character of the electronic states.

Abstract: Angle-resolved photoemission spectroscopy was performed on a ruthenate superconductor S${\mathrm{r}}_{2}$Ru${\mathrm{O}}_{4}$ ( ${T}_{c}\ensuremath{\sim}1$ K) which has the same crystal structure as L${\mathrm{a}}_{2}$Cu${\mathrm{O}}_{4}$, but with Ru${\mathrm{O}}_{2}$ layers replacing Cu${\mathrm{O}}_{2}$ layers. S${\mathrm{r}}_{2}$Ru${\mathrm{O}}_{4}$ shows an extended Van Hove singularity (VHS) at $20\ifmmode\pm\else\textpm\fi{}2$ meV below ${E}_{F}$ just like the cuprates, regardless of the character of the electronic states at ${E}_{F}$. This suggests that the extended VHS is a general feature of a two-dimensional correlated d-electron metal. The observed Fermi surface is in contrast to local-density-approximation calculations.