T -square electric resistivity and its thermal counterpart in RuO 2

We present a study of low-temperature electric and thermal transport in RuO₂, a metallic oxide which has attracted much recent attention. Careful scrutiny of electric resistivity reveals a quadratic temperature dependence below 20 K undetected in previous studies of electronic transport in this material. The prefactor of this T^2 resistivity, given the electronic specific heat, corresponds to what is expected by the Kadowaki-Woods scaling. The variation of its amplitude across four different samples is negligible despite an eightfold variation of residual resistivity. There is also a T^5 resistivity due to scattering by phonons. By measuring thermal conductivity at zero field and at 12 T, we separate its electronic and phononic components and find that the former respects the Wiedemann-Franz law at zero temperature and deviates downward at finite temperature. The latter corresponds to a threefold discrepancy between the prefactors of the two (thermal and electric) T-square resistivities. Our results, establishing RuO₂ as a weakly correlated Fermi liquid, provide input for the ongoing theoretical attempt to give a quantitative account of electron-electron scattering in metallic oxides starting from first principles.