A PHOTOEMISSION SPECTROSCOPY STUDY OF PRNIO3 THROUGH THE METAL-INSULATOR-TRANSITION

In this paper we report ultraviolet photoemission data from PrNiO3, th e first member of the rare-earth nickelate series to undergo a metal-t o-insulator transition at a finite temperature, T-MI Photoemission spe ctra 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 a t T-MI. A discontinuity in the slope of the integrated photoemission s ignal from the immediate Fermi level region allows an exact determinat ion of T-MI. Near Fermi level spectra from LaNiO3, which does not exhi bit a metal-to-insulator transition, are shown alongside the PrNiO3 da ta for comparison.