We revisit the normal-state electronic structure of ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ by angle-resolved photoemission spectroscopy with improved data quality, as well as ab initio band structure calculations in the local-density approximation with the inclusion of spin-orbit coupling. We find that the current model of a single surface layer $(\sqrt{2}\times \sqrt{2})R45°$ reconstruction does not explain all detected features. The observed depth-dependent signal degradation, together with the close quantitative agreement with the slab calculations based on the surface crystal structure as determined by low-energy electron diffraction, reveal that—at a minimum—the subsurface layer also undergoes a similar although weaker reconstruction. This model accounts for all features—a key step in understanding the electronic structure—and indicates a surface-to-bulk progression of the electronic states driven by structural instabilities. Finally, we find no evidence for other phases stemming from either topological bulk properties or, alternatively, the interplay between spin-orbit coupling and the broken symmetry of the surface.

• Received 25 May 2012

DOI:https://doi.org/10.1103/PhysRevLett.110.097004