Berry curvature dipole and nonlinear Hall effect in two-dimensional Nb_2n+1SinTe_4n+2

Recent experiments have demonstrated interesting physics in a family of two-dimensional composition -tunable materials Nb2n+1SinTe4n+2. Here we show that, owing to their intrinsic low symmetry, metallic nature, tunable composition, and ambient stability, these materials offer a good platform for studying the Berry curvature dipole (BCD) and nonlinear Hall effect. Using first-principles calculations, we find that the BCD exhibits pronounced peaks in monolayer Nb3SiTe6 (the n = 1 case). Its magnitude decreases monotonically with n and completely vanishes in the n -> infinity limit. This variation manifests a special hidden dimensional crossover of the low-energy electronic states in this system. The resulting nonlinear Hall response from the BCD in these materials is discussed. Our work reveals pronounced geometric quantities and nonlinear transport physics in Nb2n+1SinTe4n+2 family materials, which should be readily detected in experiment.