A combination of density functional and dynamical mean field theory calculations are used to show that the remarkable metal-insulator transition in the rare earth nickelate perovskites arise from a site-selective Mott phase, in which the d-electrons on a half of the Ni ions are localized to form a fluctuating moment while the d-electrons on other Ni ions form a singlet with holes on the surrounding oxygen ions. The calculation reproduces key features observed in the nickelate materials, including an insulating gap in the paramagnetic state, a strong variation of static magnetic moments among Ni sites and an absence of "charge order". A connection between structure and insulating behavior is documented. The site-selective Mott transition may be a more broadly applicable concept in the description of correlated materials.
@article{arxiv.1206.2822,
title = {Site-selective Mott transition in rare earth nickelates},
author = {Hyowon Park and Andrew J. Millis and Chris A. Marianetti},
journal= {arXiv preprint arXiv:1206.2822},
year = {2013}
}