Floquet Topological Insulator in Semiconductor Quantum Wells

Understand

Topological phase transitions between a conventional insulator and a state of matter with topological properties have been proposed and observed in mercury telluride - cadmium telluride quantum wells.

• We show that a topological state can be induced in such a device, initially in the trivial phase, by irradiation with microwave frequencies, without closing the gap and crossing the phase transition.
• We show that the quasi-energy spectrum exhibits a single pair of helical edge states.
• The velocity of the edge states can be tuned by adjusting the intensity of the microwave radiation.