Ultrafast carrier dynamics and nonlinear optical absorption of two-dimensional NiPS3 nanosheets

Two-dimensional (2D) materials have been extensively explored for various optoelectronic devices, showing tremendous application potential. Metal phosphorus trichalcogenide compounds are new intrinsic magnetic semiconductor materials that possess unique and excellent physical and optical properties. Among them, NiPS3 has a bandgap of 1.6 eV and is an intrinsic antiferromagnetic semiconductor. In our work, the nonlinear optical absorption and carrier dynamics of 2D NiPS3 nanosheets are studied by the I-scan system and time-resolved transient transmission spectroscopy. The thickness-dependent carrier relaxation time is obtained utilizing the pump-probe technique. The strong dependence of slow relaxation time on incident intensity is also reflected in the thick sample, which distinguishes the lattice thermal diffusion in 2D nanosheets from that of bulk. The saturation absorption and two-photon absorption coefficients are further achieved. Our results provide a perspective for the applications of NiPS3 nanosheets in optical devices such as micro saturable absorbers and on-chip ultrafast optical switches.