Hard X-ray core-level photoemission of V2O3

Abstract

We study the Mott-Hubbard metal-insulator transition insingle-crystal V2O3 using hard X-ray(HX: hν = 5940 eV) core-level photoemissionspectroscopy (PES). HX-PES enables a bulk probe of the electronicstructure in the paramagnetic metallic and antiferromagneticinsulating phases. Metallic V2O3 shows additionalfeatures at low binding energy to the main peak of V 1s, 2p,and 3s core levels, which vanish in the insulating phase. Thelow-binding-energy features in the metallic phase are alsoobserved using soft X-rays (SX: hν = 1450 eV), but witha reduced relative intensity compared to the HX-PES spectrum. Amodel cluster calculation including core hole screening bycoherent states at the Fermi level, reproduces thelow-binding-energy features in the metallic phase. The O 1score level also shows spectral changes: the asymmetric line shapein the metallic phase transforms to a symmetric line shape in theinsulating phase, consistent with the metal-insulator transition.The results indicate screening by coherent states is moreeffective in the bulk compared to the surface. HX-PES is, thus, areliable probe of the electronic-structure changes across themetal-insulator transition in strongly correlated electronsystems.