Stacking controllable ferrovalleys in bilayer Janus FeBrCl.

Valleytronics is an emerging concept for next-generation electronics, in which the valley anomalous Hall effect and the layer-polarized anomalous Hall effect have attracted considerable attention. However, the development of valleytronic devices is hindered by two major challenges: limited valley splitting energy and valley states relying on external magnetic fields for switching. Based on first-principles calculations, we systematically investigated the effects of stacking orders and magnetic orders on valley polarization in bilayer Janus FeBrCl. The calculation results demonstrate that by tuning the stacking and magnetic orders in bilayer Janus FeBrCl, we achieved six different stacking orders and the influence of interlayer coupling on valley polarization was studied. This enables the material's properties to evolve from a non-switchable valley-layer-locked state to an electrically switchable layer-valley coupling state, with the CBC-3R stacking configuration being a prime example of the latter, achieving a controllable valley-layer Hall effect and producing a large valley splitting (around 117 meV). These findings offer a feasible strategy for designing low-power valleytronic devices with electrically controllable valley degrees of freedom.