Quantum anomalous Hall effect and half-metal state of valley in VGe2N4 monolayer

Abstract Understanding the physical properties of valley and achieving its half metal state is the key to applying the valley degree of freedom. In this study, by first-principles calculations, the VGe 2 N 4 monolayer is demonstrated as a ferrovalley semiconductor with a valley polarization of 48 meV. Furthermore, two means of compressive strain and regulating the electron correlation effect are explored to achieve the half-metal state of valley in the present VGe 2 N 4 monolayer. Interestingly, topological phase transitions from ferrovalley, half-valley metal to quantum anomalous Hall effect state appear with the increase of strain in the VGe 2 N 4 monolayer. More interestingly, half-metal state of valley induced by electronic correlation or strain can occur in VGe 2 N 4 monolayer, which means 100% spin-polarized valley carriers will be excited. In this case, with the action of an in-plane electric field, the VGe 2 N 4 monolayer will present an anomalous valley Hall effect. Based on these results, the related valleytronics devices are designed. Our work emphasizes the entire process from ferrovalley to topological phase transition, and a method for achieving the half-metal state of valley is proposed. Our finding is of great significance for the development of valleytronics.