Origin of metal-insulator transitions in correlated perovskite metals

The mechanisms that drive metal-to-insulator transitions (MIT) in correlated solids are not fully understood, though intricate couplings of charge, spin, orbital, and lattice degrees freedom have been implicated. For example, the perovskite SrCoO3 is a ferromagnetic metal, while oxygen-deficient (n-doped) brownmillerite SrCoO2.5 an antiferromagnetic insulator. Given magnetic structural accompany MIT, driving force for such MIT transition unclear. We also observe that, interestingly, metals LaNiO3, SrFeO3, undergo when n-doped via high-to-low valence compositional changes, i.e., Ni3+?Fe4+, Sr2+?La3+, respectively. On other hand, pressurizing insulating phase drives gap closing. Here we demonstrate ABO3 perovskites most prone to self-hole-doped materials, reminiscent negative charge-transfer using combination density functional fixed-node diffusion quantum Monte Carlo calculations. Upon n doping metallic phase, underlying charge-lattice (or electron-phonon) coupling metal charge bond-disproportionated gapped state, thereby achieving ligand-hole passivation at certain sites only. size band linearly with degree hole these ligand sites. Further, metallization pressure stabilized by similar increase hole, which turn stabilizes coupling. These results suggest interaction band-gap opening realize even energy, it couples phonons enable phase. Other orderings (magnetic, orbital etc.) driven weaker interactions may assist openings low levels, but energy predominantly determines gap, preferring This can be achieved modulations oxygen stoichiometry or composition pressure. Hence, controlling amount set key factor MIT.Received 16 July 2021Accepted 24 January 2022DOI:https://doi.org/10.1103/PhysRevResearch.4.L022005Published American Physical Society under terms Creative Commons Attribution 4.0 International license. Further distribution this work must maintain attribution author(s) published article's title, journal citation, DOI.Published SocietyPhysics Subject Headings (PhySH)Research AreasMetal-insulator transitionPhysical SystemsPerovskitesTransition oxidesTechniquesDensity theoryDiffusion CarloElectron-correlation calculationsCondensed Matter, Materials & Applied Physics