Valley Polarization in Monolayer Ferromagnetic FeCl: A First-Principles Study

Valleytronics has gradually attracted people's attention for providing new degrees of freedom to future electronic devices. Herein, it is proposed that valley polarization can be realized in 2D ferromagnetic FeCl with a square lattice. The first-principles calculations without spin-orbital coupling (SOC) show that 2D FeCl is a spin-polarized semimetal material, and the crossing points around the Fermi level are protected by mirror symmetry. When considering SOC, local bandgaps open around the Fermi level, and further calculations reveal that the Berry curvatures are opposite in sign around these gaps along with different high-symmetry directions. By integrating the Berry curvature around these local extreme points, the Chern numbers of two valleys are approximate to -1/4 and 1/4, respectively, and the corresponding valley Chern numberC(v)is approximately equal to 1/2. This indicates that FeCl has the potential to realize the valley Hall effect (VHE) and will be a promising material in future valleytronics.