Double perovskite heterostructures: Magnetism, Chern bands, and Chern insulators

摘要

Experiments demonstrating the controlled growth of oxide heterostructureshave raised the prospect of realizing topologically nontrivial states ofcorrelated electrons in low dimensions. Here, we study heterostructuresconsisting of {111}-bilayers of double perovskites separated by inert bandinsulators. In bulk, these double perovskites have well-defined local momentsinteracting with itinerant electrons leading to high temperatureferromagnetism. Incorporating spin-orbit coupling in the two-dimensionalhoneycomb geometry of a {111}-bilayer, we find a rich phase diagram withtunable ferromagnetic order, topological Chern bands, and a C=2 Chern insulatorregime. An effective two-band model of Zeeman-split j=3/2 states captures thisnontrivial band topology. Our results are of broad relevance to oxide materialssuch as Sr2FeMoO6, Ba2FeReO6, and Sr2CrWO6.