Ultrafast transient sub-bandgap absorption of monolayer MoS2

Susobhan Das*, Yadong Wang, Yunyun Dai, Shisheng Li, Zhipei Sun

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

The light–matter interaction in materials is of remarkable interest for various photonic and optoelectronic applications, which is intrinsically determined by the bandgap of the materials involved. To extend the applications beyond the bandgap limit, it is of great significance to study the light–matter interaction below the material bandgap. Here, we report the ultrafast transient absorption of monolayer molybdenum disulfide in its sub-bandgap region from ~0.86 µm to 1.4 µm. Even though this spectral range is below the bandgap, we observe a significant absorbance enhancement up to ~4.2% in the monolayer molybdenum disulfide (comparable to its absorption within the bandgap region) due to pump-induced absorption by the excited carrier states. The different rise times of the transient absorption at different wavelengths indicate the various contributions of the different carrier states (i.e., real carrier states in the short-wavelength region of ~<1 µm, and exciton states in the long wavelength region of ~>1 µm). Our results elucidate the fundamental understanding regarding the optical properties, excited carrier states, and carrier dynamics in the technologically important near-infrared region, which potentially leads to various photonic and optoelectronic applications (e.g., excited-state-based photodetectors and modulators) of two-dimensional materials and their heterostructures beyond their intrinsic bandgap limitations.

Original languageEnglish
Article number27
Number of pages9
JournalLight: Science and Applications
Volume10
Issue number1
DOIs
Publication statusPublished - Dec 2021
MoE publication typeA1 Journal article-refereed

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