Evolution of a band insulating phase from a correlated metallic phase

Abstract

We investigate the evolution of the electronic structure in SrRu_1-xTi_xO₃ as a function of x using high resolution photoemission spectroscopy, where SrRuO₃ is a weakly correlated metal and SrTiO₃ is a band insulator. The surface spectra exhibit a metal-insulator transition at x = 0.5 by opening up a soft gap. A hard gap appears at higher x values consistent with the transport properties. In contrast, the bulk spectra reveal a pseudogap at the Fermi level, and unusual evolution exhibiting an apparent broadening of the coherent feature and subsequent decrease in intensity of the lower Hubbard band with the increase in x. Interestingly, the first principle approaches are found to be sufficient to capture anomalous evolutions at high energy scale. Analysis of the spectral lineshape indicates strong interplay between disorder and electron correlation in the electronic properties of this system.