Intrinsic Valley-Polarized Quantum Anomalous Hall Effect and Controllable Topological Phase Transition in Janus Fe₂SSe

Abstract

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 Fe2SSe. Spontaneous valley polarization (VP) appears without external manipulations due to the Janus structure in monolayer Fe2SSe. The spontaneous VP in addition to the nonzero Chern number in Fe2SSe 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 Fe2SSe, 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 Fe2SSe, which provides an avenue for the applications of dissipationless valleytronic devices.

Recent progress on valley polarization and valley-polarized topological states in two-dimensional materials

“…In Janus ML Fe 2 SSe, valley polarization can occur spontaneously without any external manipulation. [72] In Fe 2 SSe, because of the non-zero Chern number, the phenomenon of spontaneous valley polarization is confirmed to be inherent valley polarized QAHE. In addition, the chiral-spinvalley locked edge state of the topological protection can be adjusted by reversing the magnetization.…”

Two-dimensional magnetic Janus monolayers and their van der Waals heterostructures: a review on recent progress

“…7(e and f)]. 140 When the orientation of magnetization is along +z and Àz, the spin-down and -up electrons are conducted in the edge states 96 Copyright 2021 American Physical Society. Panels (c and d) are reproduced with permission.…”

“…7(e and f)]. 140 When the orientation of magnetization is along + z and − z , the spin-down and -up electrons are conducted in the edge states with different chiralities, respectively, leading to nonzero Chen numbers with opposite signs. Since the spin channel and electron movement are locked by SOC, the spin-polarized edge Hall current can be reversed by the orientation of magnetization.…”

“…Copyright 2021 AIP Publishing. Panels (e and f) are reproduced with permission 140. Copyright 2022 American Chemical Society.…”

Strain-driven topological quantum phase transition in (pseudo)cubic (mixed)-Cs/MA/FA halide perovskites

“…Among these phases, topological insulators are some of the most promising materials for application in spintronics due to their conducting surface states within the bulk band gap. [10][11][12][13][14][15] Numerous materials like Bi-based selenides and tellurides, 16,17 skutterudites, 18 Heusler compounds, 19,20 and Bi-based oxide perovskites (ABiO 3 ) [21][22][23] have been extensively explored for non-trivial topology. More recently, halide perovskites have also attracted the attention of researchers in the area of band topology.…”