Electron-lattice interplay in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>LaMnO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math> from canonical Jahn-Teller distortion notations
Michaël Schmitt, Yajun Zhang, Alain Mercy, Philippe Ghosez
Abstract
${\mathrm{LaMnO}}_{3}$ is considered as a prototypical Jahn-Teller perovskite compound, exhibiting a metal-to-insulator transition at ${T}_{JT}=750$ K related to the joint appearance of an electronic orbital-ordering and a large lattice Jahn-Teller distortion. From first principles, we revisit the behavior of ${\mathrm{LaMnO}}_{3}$ and show that it is not only prone to orbital ordering but also to charge ordering. Both charge and orbital orderings appear to be enabled by rotations of the oxygen octahedra and the subtle competition between them is monitored by a large tetragonal compressive strain, which is itself a Jahn-Teller active distortion. Equally, the competition of ferromagnetic and antiferromagnetic orders is dependent on the same tetragonal strain. Our results further indicate that the metal-to-insulator transition can be thought as a Peierls transition that is enabled by spin symmetry breaking. Therefore, dynamical spin fluctuations in the paramagnetic state stabilize the insulating phase by the instantaneous symmetry breaking they produce and which is properly captured from static density functional theory calculations. As a basis to our discussion, we introduce canonical notations for lattice distortions in perovskites that distort the oxygen octahedra and are connected to charge and orbital orderings.