Transient Terahertz Spectroscopy for2DMaterials

Time-resolved, pulsed terahertz (THz) spectroscopy emerged as a powerful tool for investigating the electronic and optical properties of two-dimensional (2D) materials over the past decades. As an electromagnetic wave covering the energy range from a few to about 100 meV, THz radiation bridges the electromagnetic spectrum from the optical to the electronic frequency range. It is particularly sensitive to the response of charge quasiparticles, e.g. free carriers, polarons, and excitons. The distinct spectral signatures of these different quasiparticles in the THz range allow their discrimination and characterization using pulsed THz radiation. This frequency region is also well suited for the investigation of phonon resonances and intraband transitions in low-dimensional systems. Transient THz spectroscopy provides high temporal resolution and sensitivity to ultrafast carrier dynamics, enabling the characterization of charge carrier lifetimes, carrier mobility, and ultrafast dynamics of quasiparticles in 2D materials. In this section, the latest development and analysis techniques in the application of THz time-domain spectroscopy to 2D materials are reviewed. We also discussed the challenges and future prospects of transient THz spectroscopy for 2D materials.