TY - JOUR AU - Zang, Yanmei AU - Ma, Yandong AU - Peng, Rui AU - Wang, Hao AU - Huang, Baibiao AU - Dai, Ying PY - 2021 TI - Large valley-polarized state in single-layer NbX2 (X = S, Se): Theoretical prediction JO - Nano Research SN - 1998-0124 SP - 834 EP - 839 VL - 14 IS - 3 AB - 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 ~ 156 meV/NbSe2 ~ 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 NbX2 is switchable via applying moderate strain. These findings make single-layer NbX2 tantalizing candidates for realizing high-performance and controllable valleytronic devices. UR - https://doi.org/10.1007/s12274-020-3121-1 DO - 10.1007/s12274-020-3121-1