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arXiv · 1911.04826

Phonon-assisted processes in the ultraviolet transient optical response of graphene

Dino Novko·Marko Kralj
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Abstract

Many recent experiments investigated potential and attractive means of modifying many-body interactions in two-dimensional materials through time-resolved spectroscopy techniques. However, the role of ultrafast phonon-assisted processes in two-dimensional systems is rarely discussed in depth. Here, we investigate the role of electron-phonon interaction in the transient optical absorption of graphene by means of first-principles methods. It is shown at equilibrium that the phonon-assisted transitions renormalize significantly the electronic structure. As a result, absorption peak around the Van Hove singularity broadens and redshifts by around 100\,meV. In addition, temperature increase and chemical doping are shown to notably enhance these phonon-assisted features. In the photoinduced transient response we obtain spectral changes in close agreement with the experiments, and we associate them to the strong renormalization of occupied and unoccupied $π$ bands, which predominantly comes from the coupling with the zone-center $E_{2g}$ optical phonon. Our estimation of the Coulomb interaction effects shows that the phonon-assisted processes can have a dominant role even in the subpicosecond regime.

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Dino Novko, Marko Kralj. 2019-11-12. Phonon-assisted processes in the ultraviolet transient optical response of graphene. https://doi.org/10.1038/s41699-019-0131-5

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