Topological electronics and topological field effect transistor in silicene, germanene and stanene

We report the recent progress on the theoretical aspects of monolayer topological insulators including silicene, germanene and stanene. They are monolayer honeycomb structures of silicon, germanium and tin, respectively. They show quantum spin Hall effects in nature due to the spin orbit interaction. The band gap can be tuned by applying perpendicular electric field. It may cause a topological phase transition, which makes the helical edge states inherent to the quantum spin Hall phase disappear. We propose to employ this phenomenon as the key mechanism of a topological field effect transistor, where the conductance is switched off by applying electric field. The conductance is always quantized and robust against impurities and randomness due to the topological protection, which is highly contrasted with the case of ordinary transistor. Our results will open a new field of topological electronics.