Band structures calculated by using TB models with silicene hopping strength t = 1.6 eV. The parameters adopted are (a) U = M = 0.0 eV; (b) U = 0.18 eV, M = 0.0 eV; and (c) U = 0.18 eV, M = 0.25. When the SOC is included, bands in panel (d) are obtained. The arrows in panel (d) represent the spin directions. Reprinted with permission from Ref. [20]. Copyright 2013 by the American Physical Society.