Linear optical and electronic properties of the polar metallic ruthenate (Sr,Ca)Ru2O6.

Using first-principles calculations, we compute the linear optical properties for cation ordered (Sr,Ca)Ru2O6. Our calculations show that this polar ferromagnetic metallic oxide exhibits optical anisotropy along the principal directions of the optical indicatrix owing to the absence of inversion symmetry in the crystal structure. The calculated reflectivity is used to locate the onset of the inter-band transitions at an energy of 1.3 eV. Comparing the optical conductivity with the electronic band structure, we identify the possible optical transitions. Finally, we apply the generalized Drude model to deduce an enhancement of the effective mass, m(*) ∼ 4.9m(e), in ordered (Sr,Ca)Ru2O6. Moreover, we show that removal of the polar distortions decrease the effective mass to m(*) ∼ 4.4m(e), suggesting that control over the amplitude of the polar displacements could be used to tune the degree of electronic correlation in oxide conductors without inversion symmetry.