Quasi-two-dimensional van der Waals semiconducting magnet CrSiTe₃ studied by using THz spectroscopy

Quasi-two-dimensional van der Waals ferromagnetic semiconductor CrSiTe₃ with wide potential applications in optoelectronics and nanospintronics has aroused the immense interest of researchers due to the coexistence of intrinsic magnetism and semiconductivity. By combining untrafast femtosecond laser and terahertz spectroscopy, including terahertz time-domain spectroscopy, optical pump-terahertz probe spectroscopy and terahertz emission spectroscopy, we carry out systematic investigation into the van der Waals ferromagnetic semiconductor CrSiTe₃ crystal. The experimental results indicate that the conductivity of the sample is robust against the temperature change and isotropic terahertz transmission in the <i>ab</i>-plane. Moreover, it is also observed that the photocarriers induced by 800 nm optical pump exhibit a relaxation in the biexponential form and the complex photoconductivity can be well reproduced by the Drude-Smith model. The main relaxation channel of photocarriers is the recombination of electron-hole pairs. With femtosecond pulse illuminating the surface of sample, a strong terahertz radiation signal with a broad band of 0–2 THz is observed. The present study provides the responses of CrSiTe₃ to optical and terahertz frequency and offers crucial information for the future design of CrSiTe₃-based electronic and optoelectronic devices.