Edge-state mechanism for the anomalous quantum Hall effect in a diatomic square lattice

The understanding of the Chern insulator and anomalous quantum Hall effect (AQHE) in terms of chiral edge states in confined systems is the first aim of the paper. The model we use consists in a diatomic square lattice with hopping to the next-nearest-neighbors and broken time-reversal symmetry, which exhibits edge states in the absence of an external magnetic field. The question of chiral edge states is approached in the ribbon and plaquette geometries with different atomic connectivities at the boundaries. Insulating and semi-metallic phases are revealed, the resulting phase diagram being richer than in Haldane's model. The transmission coefficients and the Hall resistance $R_H$ are calculated for the finite size system in the Landauer-B\"{u}ttiker formalism. The quantized values $R_H=\pm h/e^2$, specific to the Chern insulator, are manifest in the energy range occupied by the chiral edge states, corresponding to the unique gap existing in the energy spectrum. Our second aim is to examine the disorder-induced properties of the model, and, as a novelty, we prove the disorder-driven AQHE in the semi-metallic phase.