  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.
