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

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 Ni3⁺ ions with a 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.