Three-band Hubbard model for Na2IrO3 : Topological insulator, zigzag antiferromagnet, and Kitaev-Heisenberg material

Na${}₂$IrO${}₃$ is a promising material to realize Kitaev physics in nature. Even though it shows long-range magnetic order of antiferromagnetic zigzag type at low temperature, the Kitaev interaction has been predicted to be significant. The origin of zigzag order, however, is currently still debated. Here, the authors suggest that adding charge fluctuations to the Kitaev-Heisenberg (KH) model represents an interesting explanation of zigzag antiferromagnetism. Moreover, their phenomenological three-band Hubbard model puts this material into a larger context as it combines topological insulator physics for weak electron interactions and KH physics for strong ones.