Exceptionally High Nonlinear Optical Response in Two‐dimensional Type II Dirac Semimetal Nickel Di‐Telluride (NiTe 2 )

Nickel ditelluride (NiTe 2 ) is a newly identified Type‐II Dirac semimetal, showing novel characteristics in electronic transport and optical experiments. This study explores the nonlinear optical properties of 2D NiTe 2 using experimental and computational techniques (density functional theory‐based approach). Few layered 2D‐NiTe 2 are synthesized using liquid phase exfoliation (LPE), which is characterized using X‐ray diffraction technique, transmission electron, and atomic force microscopy. The nonlinear refractive index () and third‐order nonlinear susceptibility () of the prepared 2D‐NiTe 2 are determined from the self‐induced diffraction pattern generated using different wavelengths (λ = 650, 532, and 405 nm) in the far field. In addition, the diffraction pattern generated by spatial self‐phase modulation (SSPM) is further verified by varying concentration (2D‐NiTe 2 in the IPA solvent), wavelength (of incoming laser beams), and cuvette width (active path length). The high value of third‐order nonlinear susceptibility for a monolayer (in order of ×10 −9 e.s.u.) determined using SSPM in the 2D‐NiTe 2 can be attributed to the laser‐induced hole coherence effect. Last, utilizing the reverse saturable absorption property of 2D‐hBN, asymmetric light propagation is also demonstrated in the 2D‐NiTe 2 /2D‐hBN heterostructure.