Observation of particle hole asymmetry and phonon excitations in non-Fermi-liquid systems: a high-resolution photoemission study of ruthenates

Abstract

We investigate the temperature evolution of the electronic states in the vicinity of the Fermi level of a non-Fermi-liquid (NFL) system, CaRuO₃ using ultra high-resolution photoemission spectroscopy; isostructural SrRuO₃ exhibiting Fermi-liquid behavior despite similar electron interaction parameters as that of CaRuO₃, is used as a reference. High-energy resolution in this study helps to reveal particle-hole asymmetry in the excitation spectra of CaRuO₃ in contrast to that in SrRuO₃. In addition, we observe signature of phonon excitations in the photoemission spectra of CaRuO₃ at finite temperatures while these are weak in SrRuO₃.