Charge correlation in V2OPO4 probed by hard X-ray photoemission spectroscopy

Electronic properties of V2OPO4 have been investigated by means of hard X-ray photoemission spectroscopy (HAXPES) and subsequent theoretical calculations. The V 1s and 2p HAXPES spectra are consistent with the charge ordering of V2+ and V3+. The binding energy difference between the V2+ and V3+ components is unexpectedly large, indicating large bonding-antibonding splitting between them in the final states of core level photoemission. The V 1s HAXPES spectrum exhibits a charge transfer satellite which can be analyzed by configuration interaction calculations on a V2O9 cluster. The V 3d spectral weight near the Fermi level is assigned to the 3dt2g orbitals of the V2+ site. The broad V 3d spectral distribution is consistent with the strong hybridization between V2+ and V3+ in the ground state. The core level and valence band HAXPES results indicate substantial charge transfer from the V2+ site to the V3+ site.