Possible interaction driven topological phases in (111) bilayers of LaNiO3

TL;DR

This study uses a variational mean-field approach to explore the phase diagram of LaNiO3 bilayers grown along the (111) direction, revealing emergent topological phases driven by electron interactions.

Contribution

It demonstrates the emergence of topological phases, including a quantum anomalous Hall insulator, in LaNiO3 bilayers as a function of interaction strength and Hund's coupling.

Findings

Identification of a Dirac half-semimetal phase.

Discovery of a quantum anomalous Hall insulator with Chern number one.

Observation of a ferromagnetic nematic phase breaking lattice symmetry.

Abstract

We use the variational mean-field approach to systematically study the phase diagram of a bilayer heterostructure of the correlated transition metal oxide LaNiO3, grown along the (111) direction. The Ni 3+ ions with d7 (or eg1) configuration form a buckled honeycomb lattice. We show that as a function of the strength of the on-site interactions, various topological phases emerge. In the presence of a reasonable size of the Hund's coupling, as the correlation is tuned from intermediate to strong, the following sequence of phases is found: (1) a Dirac half-semimetal phase, (2) a quantum anomalous hall insulator (QAHI) phase with Chern number one, and (3) a ferromagnetic nematic phase breaking the lattice point group symmetry. The spin-orbit couplings and magnetism are both dynamically generated in the QAHI phase.