High-resolution photoemission study ofV2−yO3

Abstract

High-resolution photoemission spectroscopy (HRPES) was performed on ${\mathrm{V}}_{2\ensuremath{-}y}{\mathrm{O}}_{3}$ ($y$=0.00, 0.03, and 0.04), which has been considered as the prototype of the Mott-Hubbard model for the metal-insulator transition (MIT). The density of states at the Fermi level ${(E}_{\mathrm{F}})$ observed by HRPES is one order of magnitude smaller than that of the band calculation based on the local-density approximation. We observed no distinguishable sharp structure at ${E}_{\mathrm{F}}$ for hole-doped ${\mathrm{V}}_{1.96}{\mathrm{O}}_{3}$ at 15 K as well as negligible temperature-dependence of the HRPES spectrum of ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ between 200 and 300 K. The analysis of the V 3$d$ spectrum with a local self-energy gives a too large quasiparticle effective mass compared to the specific-heat measurement, which implies the importance of spatial fluctuations near the MIT. All these facts strongly question the applicability of the dynamical mean-field theory of the Hubbard model to the ${\mathrm{V}}_{2\ensuremath{-}y}{\mathrm{O}}_{3}$ system.