The Role of Electronic and Phononic Excitation in the Optical Response of Monolayer WS<sub>2</sub> after Ultrafast Excitation.

Ruppert, Claudia; Chernikov, Alexey; Hill, Heather M; Rigosi, Albert F; Heinz, Tony F · Nano Lett · 2017

basic_science · Level V

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Abstract

Transient changes of the optical response of WS<sub>2</sub> monolayers are studied by femtosecond broadband pump-probe spectroscopy. Time-dependent absorption spectra are analyzed by tracking the line width broadening, bleaching, and energy shift of the main exciton resonance as a function of time delay after the excitation. Two main sources for the pump-induced changes of the optical response are identified. Specifically, we find an interplay between modifications induced by many-body interactions from photoexcited carriers and by the subsequent transfer of the excitation to the phonon system followed by cooling of the material through the heat transfer to the substrate.