Mechanism of ferromagnetism and valley properties in monolayer TiSeCl

Abstract

We introduce a novel two-dimensional ferromagnetic valley material, TiSeCl, and confirm its potential to enable valley-related multichannel Hall effects within a stable two-dimensional ferromagnetic semiconductor. The intrinsic lack of spatial inversion symmetry and time-reversal symmetry in the TiSeCl structure allows for spontaneous valley polarization, making it highly advantageous for practical valley manipulation since its intrinsic valley polarization values can reach 95 meV. The strong spin–orbit coupling effects in the TiSeCl monolayer result in distinct Berry curvatures and opposing signals in the +K and −K valleys, leading to an anomalous valley Hall effect. Furthermore, under a 1.25% tensile strain, the TiSeCl monolayer undergoes band inversion, leading to a topological phase transition from the ferromagnetic valley state to the semivalley metal state and subsequently to a valley-polarized quantum anomalous Hall phase. This study expands our understanding of valley properties in two-dimensional materials and provides theoretical guidance for valley manipulation in valley electronics.