Switchable valley-contrasting Berry curvature in two-dimensional valley-semi-half-metals

Generating and controlling valley-contrasting Berry curvature in two-dimensional (2D) hexagonal magnetic materials holds significant promise for advancements in spintronics and valleytronics. Here, we explore the interplay between valley index, magnetic ordering, and band topology in a single 2D semi-half-metallic system, introducing a critical state termed valley-semi-half-metal, which is crucial for realizing high Chern number quantum anomalous Hall (QAH) insulators. We identify the fluorinated 1T-CrS2 monolayer (1T-CrS2F2) as a promising material, exhibiting soft ferromagnetic characteristics ideal for achieving this 2D valley-semi-halfmetallic state. Remarkably, the monolayer 1T-CrS2F2 can transition from a semi-half-metallic state to a high Chern number QAH insulator with opposite-chiral edge states through magnetization reversal. Additionally, the Janus 1T-CrS2FCl monolayer, which lacks inversion symmetry, enables gate-tunable, valley-contrasting QAH insulator phases with opposite Chern numbers upon reversing the magnetization. Our findings highlight a promising magnetic candidate for exploring valley and topological physics, offering an alternative approach for designing switchable QAH effects and paving the way for innovative topological quantum devices.