Fermi Surface, Surface States, and Surface Reconstruction inSr2RuO4

The electronic structure of ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ is investigated by high angular resolution ARPES at several incident photon energies. We address the controversial issues of the Fermi surface (FS) topology and the van Hove singularity at the $M$ point, showing that a surface state and the replica of the primary FS due to $\sqrt{2}\times \sqrt{2}$ surface reconstruction are responsible for previous conflicting interpretations. The FS thus determined by ARPES is consistent with the de Haas–van Alphen results, and it provides additional information on the detailed shape of the $\alpha$, $\beta$, and $\gamma$ sheets.