Comparative study of low-lying excitations in cuprate and strontium ruthenate superconductors

High-Tc cuprate superconductors in their normal state are known to have the mysterious strange-metal behavior near optimal doping with strong deviations from the conventional Fermi Liquid form of electronic scattering rates. In particular, these have been described by the marginal-fermi-liquid (MFL) form at optimal doping [1], or more generally the power-law-liquid (PLL) form over all doping levels [2]. Here with careful analysis of the intrinsic line shape of Angle-resolved photoemission (ARPES) dispersion cuts, we report a comparative study of the both ω- and T- dependent scattering rate of (Pb)Bi2Sr2CaCu2O8+δ, La2-xSrxCuO4, as well as the copper-free perovskite superconductor Sr2RuO4. With a unified power-law-liquid form of the imaginary self-energy proposed by Reber et al [2], our fitted parameters reproduce the strange-metal and fermi-liquid-like behavior of the cuprate superconductors and Sr2RuO4, respectively. Surprisingly, we show a much stronger electronic coupling parameter for the scattering in the ruthenates compared to the cuprates, indicating another key difference between these different superconductors.