Realizing Haldane model in Fe-based honeycomb ferromagnetic insulators

Abstract

Condensed-matter physics: materials for Haldane model The topological Haldane model (FHM) on a honeycomb lattice describes a mechanism through which a quantum Hall effect can emerge as an intrinsic property from the band structure in the absence of an external magnetic field. Despite its simplicity, this model has proved to be challenging in the physical implementation. A team led by Hae-Young Kee at Canada’s University of Toronto proposed a way to search for realistic materials to experimentally realize the THM showing that effectively spinless fermion with complex next nearest neighbour hopping integrals can be found in ferromagnetic insulators with strong Hund’s coupling and finite spin orbital coupling. The authors suggest that a series of iron based honeycomb ferromagnetic insulators in the form of AFe2(PO4)2 (A=Ba, Cs, K and La) possess Chern bands featured by the THM. This work provides a playground for the identification of new correlated topological materials.