Time-Resolved Terahertz Spectroscopy Studies on 2D Van der Waals Materials

Owing to the fascinating and technologically useful electronic and optical properties, 2D van der Waals (vdW) materials are viewed as the key component for the next-generation optoelectronic, photovoltaic, and nanoelectronic devices. Fully understanding the ultrafast carrier dynamics in 2D vdW materials is essential to study the fundamental physics and realize potential applications. Time-resolved terahertz (THz) spectroscopy is a powerful tool used to investigate the ultrafast carrier dynamics and transport properties in semiconducting materials. In recent years, the time-domain THz spectroscopy measurements, with or without photoexcitation on samples, are widely used to investigate the carrier dynamics of 2D vdW materials. A brief summary on the recent progress of time-domain THz spectroscopy studies on ultrafast dynamics processes is provided. These include exciton formation and relaxation processes in semiconducting 2D materials, the relaxation of hot electrons in graphene layers, the conductivity of 2D materials modulated by femtosecond laser pulses, and their related physical properties. Finally, the physical properties of 2D vdW materials observed using the time-domain THz spectroscopy approach are highlighted and the future challenges for time-resolved THz spectroscopy investigations on 2D vdW materials are presented.