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【Abstract】

The low-dimensional materials in the carbon family, including graphene and carbon nanotubes, show unique responses in the terahertz range of the electromagnetic spectrum. Terahertz photons carry only a few meV energy; hence, they are ideal for probing intraband scattering. After photoexcitation, strong carrier-carrier and carrier-phonon scattering happens in these materials, which shows unique characteristics in the photoconductivity spectra at the terahertz range, including negative photoconductivity, the transition from negative to positive and positive photoconductivity. The importance of diverse scattering mechanisms and the relaxation dynamics after photoexcitation will be explained. Eventually, the generation, control, and application of ultrafast photo-excited hot carriers in the biomedical field will be discussed.