Jean-Marc Triscone awarded a honorary doctorate

by the Norwegian University of Science and Technology (NTNU)

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next Q-MAC meetings in 2018:

3rd Q-MAC symposium in Venice, May 22-25, 2018.

Next regular meeting in Paris, November 27-28, 2018.

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Publication Detail / Abstract

A. Subedi, O. E. Peil, A. Georges

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

published in Physical Review B on February 25, 2015
> Full text via publisher
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.
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