Berry Curvature Dipole Induced Giant Mid-Infrared Second-Harmonic Generation in 2D Weyl Semiconductor

Due to its inversion-broken triple helix structure and the nature of Weyl semiconductor, 2D Tellurene (2D Te) is promising to possess a strong nonlinear optical response in the infrared region, which is rarely reported in 2D materials. Here, a giant nonlinear infrared response induced by large Berry curvature dipole (BCD) is demonstrated in the Weyl semiconductor 2D Te. Ultrahigh second-harmonic generation response is acquired from 2D Te with a large second-order nonlinear optical susceptibility (chi(2)), which is up to 23.3 times higher than that of monolayer MoS2 in the range of 700-1500 nm. Notably, distinct from other 2D nonlinear semiconductors, chi(2) of 2D Te increases extraordinarily with increasing wavelength and reaches up to 5.58 nm V-1 at approximate to 2300 nm, which is the best infrared performance among the reported 2D nonlinear materials. Large chi(2) of 2D Te also enables the high-intensity sum-frequency generation with an ultralow continuous-wave (CW) pump power. Theoretical calculations reveal that the exceptional performance is attributed to the presence of large BCD located at the Weyl points of 2D Te. These results unravel a new linkage between Weyl semiconductor and strong optical nonlinear responses, rendering 2D Te a competitive candidate for highly efficient nonlinear 2D semiconductors in the infrared region. Giant mid-infrared second-harmonic generation performance (better than the visible region) is demonstrated in the newly discovered Weyl semiconductor -2D Te. Theoretical calculations reveal that it originated from the large Berry curvature dipole near the Weyl points of 2D Te. Therefore, even excited by continuous-wave laser, strong sum-frequency generation can be obtained in 2D Te.image