Quantum Anomalous Hall Effect in Antiferromagnetic 4d Oxides

Quantum Anomalous Hall (QAH) insulators show quantized Hall resistance with vanishing longitudinal resistance even in the absence of an external magnetic field. Existing experimental platforms for QAH phases, primarily based on either doped or crystalline variants of 3D topological insulators, as well as moiré materials, are limited to low temperatures of a few kelvin. Finding alternative model systems and new design principles for Chern bands are imperative for realizing high-temperature QAH effects. Following our earlier theoretical proposal ^[1] based on canted collinear antiferromagnetic 5d oxides, we propose in this work a new, experimentally feasible QAH model system of 4d Ruddlesden-Popper type perovskites (A₂BC₄). The Chern bands are enabled by time-reversal-symmetry breaking in the orbital sector together with orbital-dependent hopping due to rotation of BC₆ octahedra. We give the necessary conditions for the QAH phase in such systems using first-principles-based minimal models and discuss their relevance to real materials. 

[1] Xiao Li, Allan H. MacDonald & Hua Chen, arXiv:1902.10650