Observation of a Pseudogap in the Vicinity of the Metal–Insulator Transition in the Perovskite-type Vanadium Oxides Nd1−xSrxVO3

Abstract

We have performed a photoemission study of the Mott–Hubbard system Nd1−xSrxVO3 (x = 0.20 and 0.30) to investigate the electronic structure in the vicinity of the metal–insulator transition. By using bulk sensitive hard X-ray photoemission spectroscopy, we have observed a large coherent spectral weight near the Fermi level compared to those observed with surface-sensitive low photons. In particular, a pseudogap with an energy of ∼0.2 eV has been observed near the Fermi level, which is consistent with a prediction with a dynamical cluster approximation calculation. In order to understand the characteristic features in the Mott–Hubbard-type metal–insulator transition, particularly the pseudogap opening at x = 0.2 and 0.3, a phenomenological model of the self-energy has been proposed.