Large valley polarization and high Curie temperature in single layer XI2 (X = Sc, Y)

Abstract

Ferrovalley materials with spontaneous valley polarization are the key to valleytronics applications. Therefore, it is important to find materials with relatively large valley polarization. In this work, we theoretically designed two novel two-dimensional ferrovalley materials namely XI2 (X = Sc, Y), which have both high Curie temperature and large valley polarization. The Curie temperature of monolayer ScI2 and YI2 are 138 K and 58 K, the large valley polarization of 97 meV and 108 meV are also predicted in monolayer ScI2 and YI2. The anomalous valley Hall effect is also proposed based on the valley contrasting Berry curvature. In addition, strain engineering can effectively modulate the valley polarization and Curie temperature of monolayer XI2 (X = Sc, Y). The Curie temperature of ScI2 increases with increasing strain, and the valley polarization of YI2 increases with increasing strain. Our findings suggest that monolayer XI2 (X = Sc, Y) is a promising material for valleytronics.