Valley polarized quantum Hall effect and topological insulator phase transitions in silicene

Silicene is a buckled monolayer of silicon. Its electronic properties are distinct from both the conventional two dimensional electron gas and the famous graphene due to strong spin orbit interaction and the buckled structure. Silicene has the potential to overcome limitations encountered for graphene, in particular the zero band gap and weak spin orbit interaction. We find for silicene a valley polarized quantum Hall effect and topological insulator phase transitions. We use the Kubo formalism to discuss the Hall conductivity and address the longitudinal conductivity for elastic impurity scattering in the first Born approximation. We show that the combination of an electric field with intrinsic spin orbit interaction leads to quantum phase transitions at the charge neutrality point. This provides a tool to experimentally tune the topological state of silicene. In contrast to graphene and other conventional topological insulators, the effects in silicene are experimentally accessible. Therefore, silicene constitutes a model system for exploring the spin and valley physics not accessible in graphene due to the small spin orbit interaction.