Spontaneous and tunable valley polarization in two-dimensional single-layer LaCl₂

Abstract

Applying the valley contrasting properties of valleytronic materials to logical operations is the foundation of valleytronic device manufacturing. It is predicted that single-layer LaCl2 is an ferrovalley material with intrinsic and tunable valley polarization through first-principles calculations. It is a ferromagnetic semiconductor (bandgap 0.767 eV) with roughly 1.0 μB per unit cell as well as out of plane magnetization, and the Curie temperature is about 149 K. The tight-binding model considering five orbitals as well as next nearest neighboring hopping get a consistent band structure with the first-principles calculation. The valley polarization changes from 40.49 to 98.51 meV under the biaxial strain of 5% ~ -5%. Therefore, the biaxial strain can be a means to tune the valley polarization. In addition, the valley polarization of the double-layer structure (~ 80 meV) is much greater than that of the single-layer structure (~ 59 meV) due to the increased magnetic moment of the double-layer structure, indicating the potential tunable character by stacking few layers. We believe that single-layer LaCl2 has great potential for device manufacturing and application in the field of valley electronics.