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IMAGE: a, Modulation on the Coulomb interaction. (left) Illustration of increased screening of Coulomb interactions in 2D semiconductors. (right) Schematic illustration showing the impact of increased screening of Coulomb interactions on...
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Credit: by Yuhan Wang, Zhonghui Nie, Fengqiu Wang
Two-dimensional (2D) semiconductors can host a rich set of excitonic species because of the greatly enhanced Coulomb interactions. The excitonic states can exhibit large oscillator strengths and strong light-matter interactions, and dominate the optical properties of 2D semiconductors. In addition, because of the low dimensionality, excitonic dynamics of 2D semiconductors can be more susceptible to various external stimuli, enriching the possible tailoring methods that can be exploited. Understanding the factors that can influence the dynamics of the optically-generated excited states represents an important aspect of excitonic physics in 2D semiconductors, and is also crucial for practical application as excited state lifetimes are linked to the key figures of merit of multiple optoelectronic and photonic devices. While certain experiences have been accumulated for bulk semiconductors, the atomic nature of 2D semiconductors might makes these approaches less effective or difficult to be adapted. One the other hand, the unique properties of 2D semiconductors, such as the robust excitonic states, the sensitivity to external environmental factors and flexibility in constructing vdW heterostructures, promise modulation strategies different from conventional materials.