Cr3X2Y2 (X, Y = S, Se, Te) monolayers: valley-polarized quantum anomalous Hall insulators driven by electric field

Abstract

The valley-polarized quantum anomalous Hall (VP-QAH) insulators, combining valleytronics and topology in materials, have promising applications in low-power-consumption spintronic devices. Based on a tight-binding (TB) model and first principles calculations, we predict that Cr₃X₂Y₂ (X, Y = S, Se, Te) monolayers are ferromagnetic (FM) Weyl semimetals with out-of-plane magnetization easy axes. When the spin–orbit-coupling (SOC) effect is considered, the Weyl point is opened, giving rise to a QAH effect with Chern number C = 1. Moreover, it is found that the Cr₃X₂Y₂ monolayers exhibit a VP-QAH effect when an external electric field is applied due to the breaking of the C_2xT symmetry, and the valley polarization value increases with the enhancement of the electric field. Specially, the Curie temperature, electronic structure and topological bandgap of the Cr₃X₂Y₂ monolayers can be modulated by biaxial strains. Our results suggest that these Cr₃X₂Y₂ monolayers provide a potential platform for designing spintronic devices.