Exceptionally High Nonlinear Optical Response in Two-dimensional Type II Dirac Semimetal Nickel di-Telluride (NiTe2)

TL;DR

This study investigates the nonlinear optical properties of two-dimensional NiTe2, a newly identified Type-II Dirac semimetal, revealing high third-order nonlinear susceptibility and potential for asymmetric light propagation in heterostructures.

Contribution

The paper provides experimental and computational analysis of the nonlinear optical response of 2D NiTe2, highlighting its high third-order susceptibility and demonstrating asymmetric light propagation in heterostructures.

Findings

High third-order nonlinear susceptibility (~10^-9 e.s.u.) in 2D NiTe2.

Effective use of SSPM to measure nonlinear refractive index.

Demonstration of asymmetric light propagation in NiTe2/hBN heterostructures.

Abstract

Nickel ditelluride (NiTe2) is a newly identified Type-II Dirac semimetal, showing novel characteristics in electronic transport and optical experiments. In this study, we explored the nonlinear optical properties of two-dimensional NiTe2 using experimental and computational techniques (density functional theory-based approach). Few layered two-dimensional NiTe2 (2D-NiTe2) 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-NiTe2 are determined from the self-induced diffraction pattern generated using different wavelengths ( 405, 532, and 650 nm) in the far field. In addition, the diffraction pattern generated by spatial self-phase modulation (SSPM) is further verified by varying concentration (2D-NiTe2 in the IPA solvent), wavelength (of incoming laser beams), and cuvette width (active path length). The high value of third-order nonlinear susceptibility (in order of 10-9 e.s.u.) determined using SSPM in the 2D-NiTe2 can be attributed to the laser-induced hole coherence effect. Lastly, utilizing the reverse saturable absorption property of 2D-hBN, asymmetric light propagation is also demonstrated in the 2D-NiTe2/2D-hBN heterostructure.