Correlation effects in the electronic structure ofSrRuO3

Abstract

We have measured photoemission and inverse-photoemission spectra of the ferromagnetic metal ${\mathrm{SrRuO}}_3.$ The observed Ru $4d$-derived conduction band above and below the Fermi level ${(E}_F)$ is found to be widely spread and the emission intensity at $E_F$ to be weakened compared to band-structure calculations. Here, the calculations have been made for the ferromagnetic state with the actual distorted perovskite structure. We compare the spectra with the spectral density of states (DOS) obtained by modifying the band DOS with a phenomenological self-energy correction, which is chosen to be compatible with the measured electronic specific heat coefficient $\gamma .$ Although the mass enhancement factor is only moderately large, $\sim 4.4,$ the renormalization factor Z is found to be as small as $\sim 0.08$ ${(Z}^{-1}\sim 13).$ These indicate a significant momentum dependence of the self-energy and a highly incoherent metallic state in ${\mathrm{SrRuO}}_3.$ We have also compared the photoemission and inverse-photoemission spectra taken below and above the Curie temperature, but significant changes have not been identified.