Intrinsic Valley-Polarized Quantum Anomalous Hall Effect and Controllable Topological Phase Transition in Janus Fe 2 SSe.

The valley-polarized quantum anomalous Hall effect (VP-QAHE) in topological materials, which usually is induced by applying external manipulations, has attracted intensive attention. Here, we predict the formation and regulation of the intrinsic VP-QAHE in ferromagnetic Janus monolayer Fe 2 SSe. Spontaneous valley polarization (VP) appears without external manipulations due to the Janus structure in monolayer Fe 2 SSe. The spontaneous VP in addition to the nonzero Chern number in Fe 2 SSe confirm the intrinsic VP-QAHE. Besides, the topologically protected chiral-spin-valley locking edge states can be regulated by reversing the magnetization. Topological phase transitions between metal, half-metal, topological insulator, and ferrovalley phases can be obtained by applying biaxial strains in Fe 2 SSe, and the nontrivial band gap reaches up to 441 meV. Also, the topological phase with the VP-QAHE is robust under certain conditions. Both the intrinsic VP-QAHE and controllable topological phase transitions can be achieved in Janus monolayer Fe 2 SSe, which provides an avenue for the applications of dissipationless valleytronic devices.