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Journal Article

Low-energy description of the metal-insulator transition in the rare-earth nickelates


Subedi,  A.
Theory of Complex Materials, Condensed Matter Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
Centre de Physique Théorique, Ecole Polytechnique, CNRS, 91128 Palaiseau Cedex, France;

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Subedi, A., Peil, O. E., & Georges, A. (2015). Low-energy description of the metal-insulator transition in the rare-earth nickelates. Physical Review B, 91(7): 075128. doi:10.1103/PhysRevB.91.075128.

Cite as: https://hdl.handle.net/11858/00-001M-0000-0025-0275-C
We propose a simple theoretical description of the metal-insulator transition of rare-earth nickelates. The theory involves only two orbitals per nickel site, corresponding to the low-energy antibonding eg states. In the monoclinic insulating state, bond-length disproportionation splits the manifold of eg bands, corresponding to a modulation of the effective on-site energy. We show that, when subject to a local Coulomb repulsion U and Hund's coupling J, the resulting bond-disproportionated state is a paramagnetic insulator for a wide range of interaction parameters. Furthermore, we find that when U−3J is small or negative, a spontaneous instability to bond disproportionation takes place for large enough J. This minimal theory emphasizes that a small or negative charge-transfer energy, a large Hund's coupling, and a strong coupling to bond disproportionation are the key factors underlying the transition. Experimental consequences of this theoretical picture are discussed.