Prediction of Intrinsic Valley Polarization in Single‐Layer GdX₂ (X = Br, Cl) from a First‐Principles Study

The key to manipulating valley degrees of freedom is to achieve valley polarization. Intrinsic valley polarization materials provide a new platform for the development of valleytronics. Herein, it is found that single‐layer (SL) GdX 2 (X = Br, Cl) are ferrovalley materials. Their valley polarization values are 79 and 35 meV by first‐principles calculations. In addition, SL GdBr 2 is taken as an example and its valley physical properties are studied. Its valley polarization can be effectively tuned by the external strains. When tensile strain 4% is applied, the valley polarization value of a SL of GdBr 2 can reach 107 meV. Moreover, by reversing the spin orientation of SL GdBr 2 , the valley polarization of the SL GdBr 2 can be reversed. This is very necessary for using the electron′s valley degree of freedom to encode and process information. In addition, the doping of electrons and holes has a significant effect on the valley polarization of SL GdBr 2 . The results provide a new family of ferrovalley materials GdX 2 (X = Br, Cl).