Quantized Conductance and Field-Effect Topological Quantum Transistor in Silicene Nanoribbons

Silicene (a monolayer of silicon atoms) is a quantum spin-Hall insulator, which undergoes a topological phase transition into other insulators by applying external field such as electric field, photo-irradiation and antiferromagnetic order. We investigate the electronic and transport properties of silicene nanoribbons based on the Landauer formalism. We propose to determine topological phase transitions by measuring the density of states and conductance. The conductance is quantized and changes its value when the system transforms into different phases. We show that a silicene nanoribbon near the zero energy acts as a field-effect transistor. This transistor is robust though it makes use of the minimum quantized conductance since the zero-energy edge states are topologically protected. Our findings open a new way to future topological quantum devices.