We study the effects of ${\mathrm{RuO}}_6$ rotation on Ru $4d$ band structures in metallic ${\mathrm{Ca}}_{2-x}{\mathrm{Sr}}_x{\mathrm{RuO}}_4$ ($0.5\le x\le 2$) by first-principles electronic structure calculations. We show that the ${\mathrm{RuO}}_6$ rotation leads to the strong hybridization between $d_{xy}$ and $d_{x^2-y^2}$ bands, resulting in orbital-dependent changes in the band structure. The $d_{xy}$ band near the Fermi level is significantly modified and thereby a severely reconstructed Fermi surface with nested sections appears at $x=0.5$. In contrast, the $d_{yz}$ and $d_{zx}$ bands are found to be insensitive to the rotational distortions induced by the Ca substitution. Our results imply that the progressive changes in the magnetic, optical, and thermal properties of ${\mathrm{Ca}}_{2-x}{\mathrm{Sr}}_x{\mathrm{RuO}}_4$ are associated with the $d_{xy}$ band.

• Received 12 October 2006

DOI:https://doi.org/10.1103/PhysRevLett.98.226401