Origin of the Efficient Nonlinear Optical Response of Two-Dimensional Layered CuFeTe2 Nanosheets

Two-dimensional ternary transition metal chalcogenides (TMCs) have aroused great research interest owing to outstanding semiconducting properties and diverse magnetic response. CuFeTe2, as a typical TMC, exhibits ambiguous magnetic behavior and ground state of spin density waves nature. Herein, we first report efficient nonlinear absorption and superior nonlinear refraction of CuFeTe2 nanosheets. The nonlinear absorption and refraction coefficients reach −0.22 cm/GW and −1.66 × 10–12 cm2/W, respectively. Semiempirical theory for direct bandgap semiconductors was applied to estimate the nonlinearities of CuFeTe2 nanosheets. The calculation results indicate that the efficient nonlinearities stem from the free carrier induced band filling effect.