The switchable quantum anomalous Hall effect and altermagnetism in Janus monolayer and bilayer V₂WS₂Se₂

The quantum anomalous Hall effect (QAHE), characterized by quantized Hall conductance and dissipationless chiral edge states, holds promising potential for application in low-power electronic devices. Magnetic topological insulators with high Chern number QAHE and Curie temperature above room temperature enable transformative advances in topological electronics and quantum computing. This study demonstrates the QAHE characteristics of Janus monolayer and bilayer V₂WS₂Se₂ by performing first-principles calculations. Monolayer V₂WS₂Se₂ is an intrinsic ferromagnetic (FM) topological insulator. It holds three key properties: a high Curie temperature (346 K), a large topological band gap (143 meV), and a QAHE with a Chern number C = 1. Additionally, monolayer V₂WS₂Se₂ in the antiferromagnetic (AFM) configuration displays altermagnetism with a spin splitting of 425.3 meV. More importantly, bilayer V₂WS₂Se₂ exhibits staggered spin polarization in the AFM interlayer coupled configuration, and the QAHE with Chern number C = 2 in the FM interlayer coupled configuration. These two rare characteristics are switchable via interlayer sliding. The present study proposes a mechanical way for regulating the topological phase, and a novel 2D material with profound implications for topological electronics and quantum computing.