Unusual Electronic and Optical Properties Induced by External Fields in Bilayer Silicene

The generalized tight-binding model has been developed to examine the role played by the uniform perpendicular electric and magnetic fields on electronic and optical properties for AB-bt (bottom-top) bilayer silicene. The multi-valley energy band and the absorption structures can be easily adjusted by the applied external electric field. A critical quantum phase transition occurs between metallic and semiconducting states when an electric field is applied to the system. Moreover, an electric field can dramatically change the main characteristics of Landau levels (LLs), including the LL degeneracy, the LL splitting, and the spatial distribution. This leads to the diverse magneto-absorption spectra with non-uniform absorption peaks, extra inter-LL transition channels, and special optical selection rules. These unique features are not present in other well-known two-dimensional (2D) atomic crystals.