Exploring the electronic and topological properties of single-layer VP2X2Y2 (XY= AlS, BTe, GaS): Valley polarization and quantum anomalous Hall state

Abstract

The concept of manipulating the valley degree of freedom has garnered growing attention in both fundamental scientific research and emerging applications. In this study, first-principles calculations are performed on the electronic properties and structural stability of single-layer (SL) VP2X2Y2 (XY = AlS, GaS and BTe). All three materials have been identified as ferromagnetic semiconductors, with their conduction band minimum situated at the K point. VP2Al2S2 and VP2Ga2S2, in particular, possess easy out-of-plane magnetization, thus facilitating a pronounced valley polarization observed in the bottom conduction band. Applying compressive strain can further modulate the orbital character of the bands as well as the valley polarization, leading to a transition from the bottom conduction band to the top valence band. Intriguingly, the strained SL VP2Al2S2 and VP2Ga2S2 exhibit a quantum anomalous Hall state with a nonzero Chern number of C=1, which is further evidenced by a quantized Hall conductance and a chiral gapless edge state connecting the valence and conduction bands. Thus, the unique electronic and topological properties of SL VP2X2Y2 suggest potential applications in the fields of electronics, spintronics, and valleytronics.