Structurally triggered metal-insulator transition in rare-earth nickelates and related e_g¹ perovskite

Rare-earth nickelates (RNiO3), apart for LaNiO3, exhibit on cooling a metal-insulator transition (MIT), a concurrent structural phase transition and a magnetic phase transition. Here, I first assess the ability of first-principles calculations within the DFT+U formalism to describe the properties of rare-earth nickelates. Then, using such a formalism, I show that the MIT in nickelates can be seen as a structurally triggered phase transition [1] highlighting so a first concrete example of such a kind of phase transition in simple perovskites. The origin of this unusual mechanism is then traced back in the electronic and magnetic properties, revealing a Peierls-type instability, structurally triggered by oxygen rotation motions and eventually assisted by magnetic ordering. This knowledge helps rationalizing the evolution of the MIT in thin films and heterostructures [2] and is also relevant to other e_g¹ perovskites like alkaline-earth ferrites and rare-earth manganites [3]. Work done in collaboration with A. Mercy, Y. Zhang, M. Schmitt, He Xu, J. Bieder & E. Bousquet. Research supported by ARC project AIMED and ERA.NET project SIOX. [1] A. Mercy et al., Nature Commun. 8, 1677 (2017). [2] Z. Liao et al., PNAS in press (2018). [3] Y. Zhang et al., Phys. Rev. B 98, 081108(R) (2018).