paper

Mechanism of intermetallic charge transfer and bond disproportionation in BiNiO and PbNiO revealed by hard x-ray photoemission spectroscopy

arXiv:2312.12072 · doi:10.1103/PhysRevB.109.205131

Abstract

Perovskites with Bi or Pb on the A-site host a number of interesting and yet to be understood phenomena such as negative thermal expansion in BiNiO. We employ hard x-ray photoemission spectroscopy of Ni 2 core-level as well as valence band to probe the electronic structure of BiNiO and PbNiO. The experimental results supported by theoretical calculations using dynamical mean-field theory reveal essentially identical electronic structure of the Ni-O subsystem typical of Ni charge-transfer insulators. The two materials are distinguished by filling of the Bi(Pb)-O antibonding states in the vicinity of the Fermi level, which is responsible for the Bi disproportionation in BiNiO at ambient pressure and absence of similar behavior in PbNiO. The present experiments provide evidence for this conclusion by revealing the presence/absence of Bi/Pb states at the top of the valence band in the two materials.

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