Integer Quantum Hall Effect in a Two-Orbital Square Lattice with Chern Number C=2

We investigate numerically the integer quantum Hall effect in a two-orbital square lattice. The Hall plateau \sigma _\rm H=2(e^2/h) is well defined with the Chern number C=\pm 2. With the increasing disorder, both the Hall plateau and the gap of density of states decrease gradually in width, and finally the gap disappears before vanishing of the Hall plateau. Compared with the Hall plateau induced by the external magnetic field, the one in our system is more robust against disorder. We also find that the transition from the Hall plateau to zero Hall conductance becomes sharper by increasing the size of the system.