Quarter-filled honeycomb lattice with a quantized Hall conductance

Abstract

We study a generic two-dimensional hopping model on a honeycomb lattice with strong spin-orbit coupling, $\textit{without the requirement that the half-filled lattice be a topological insulator}$. For quarter-(or three-quarter) filling, we show that a state with a quantized Hall conductance generically arises in the presence of a Zeeman field of sufficient strength. We discuss the influence of Hubbard interactions and argue that spontaneous ferromagnetism (which breaks time reversal) will occur, leading to a quantized anomalous Hall effect.