Quantum anomalous valley Hall effect in ferromagnetic MXenes with asymmetric functionalization

Abstract

The potential to detect and manipulate the valley degree of freedom within two-dimensional hexagonal lattices possessing both inversion asymmetry and time-reversal symmetry is theoretically feasible. Intrinsic ferrovalley polarization in MXenes could be induced by asymmetric surface functionalization to break their inversion symmetry and the presence of spin–orbital coupling ensures their time-reversal symmetry. Our results indicate that the ferromagnetic Cr₂COF MXene with Janus functionalization becomes an intrinsic Chern insulator with large spin–valley polarization and belongs to the family of quantum anomalous valley Hall effect (QAVHE) materials, based on Berry curvature and edge state calculations. Applying chemical engineering of functionalization to magnetic MXenes allows us to tune the structure–property relationship in 2D layers to obtain desirable spin–valley coupling. Our theoretical insight into the QAVHE on magnetic MXenes with asymmetry functionalization provides a new opportunity for valleytronics and spintronics.