A photoemission spectroscopy study of PrNiO3 through the metal-insulator transition

In this paper we report ultraviolet photoemission data from $\rm PrNiO _{3}$, the first member of the rare-earth nickelate series to undergo a metal-to-insulator transition at a finite temperature, $T _{\rm MI}$. Photoemission spectra from the Fermi level region as a function of temperature show the clear opening-up of the gap in the quasi-particle density of states at TMI. A discontinuity in the slope of the integrated photoemission signal from the immediate Fermi level region allows an exact determination of TMI. Near Fermi level spectra from $\rm LaNiO _{3}$, which does not exhibit a metal-to-insulator transition, are shown alongside the $\rm PrNiO _{3}$ data for comparison