Large valley-polarized state in single-layer NbX2 (X = S, Se): Theoretical prediction

Exploring two-dimensional valleytronic crystals with large valley-polarized state is of considerable importance due to the promising applications in next-generation information related devices. Here, we show first-principles evidence that single-layer NbX2(X = S, Se) is potentially the long-sought two-dimensional valleytronic crystal. Specifically, the valley-polarized state is found to occur spontaneously in single-layer NbX2, without needing any external tuning, which arises from their intrinsic magnetic exchange interaction and inversion asymmetry. Moreover, the strong spin-orbit coupling strength within Nb-d orbitals renders their valley-polarized states being of remarkably large (NbS2 similar to 156 meV/NbSe2 similar to 219 meV), enabling practical utilization of their valley physics accessible. In additional, it is predicted that the valley physics (i.e., anomalous valley Hall effect) in single-layer NbX(2)is switchable via applying moderate strain. These findings make single-layer NbX(2)tantalizing candidates for realizing high-performance and controllable valleytronic devices.

Automated summary

Single-layer NbX2 (X = S, Se) shows potential as a two-dimensional valleytronic crystal with large valley-polarized state, and the valley physics can be switched by applying strain. This makes them tantalizing candidates for high-performance and controllable valleytronic devices.