Speaker
Description
The low dimensional nature of transition metal dichalcogenides (TMDCs) and the resulting reduced screening significantly influence their non-equilibrium optical properties. We investigated the role of different photoexcited quasiparticles on the dynamic response of WS2 monolayers and provide a formalism that allows the quantitative comparison of exciton dynamics in TMDCs for different samples, optical sampling techniques, and substrates [1]. We then unveil the role of the presence of different quasiparticles upon resonant/above-resonance photoexcitation, by fitting a phenomenological model describing the microscopic time evolution of the photo-excited quasiparticle population to the pump energy and fluence dependence of the exciton dynamics [2].
The combination of TMDCs with organic dye molecules is promising for the next generation of optoelectronic and light harvesting devices. In this context, we studied terrylene molecules in solution and thin films both on a transparent substrate and a WS2 monolayer. The different environments change the ultrafast dynamics of terrylene drastically: Compared to the bare molecules in solution, pristine terrylene film shows absorption bands strongly blue-shifted due to H-aggregation and while photoexcitation of the aggregate leads to the formation of an induced monomer-like absorption band due to interference of the Frenkel exciton and charge-transfer (CT) state. Preliminary analysis of the hybrid terrylene/WS2 sample shows clear signs of hybridization both in steady state and transient spectroscopy.
To study femtosecond dynamics on optical energy scales and at the nanoscale, we are developing time-resolved interferometric optical nanoscopy (TRION). This will yield unprecedented observations of the spatial dependence of electron dynamics in TMDC monolayers and TMDC/organic heterojunctions with nm spatial resolution and fs temporal resolution. The poster will show first AFM and near-field images acquired using our femtosecond laser system.
References
[1] S. Calati et al., Phys. Chem. Chem. Phys. 23, 22640 (2021).
[2] S. Calati et al., under review (2022).
[3] S. Palato et al., Appl. Phys. Lett. 120, 131601 (2022).
| Abstract Number (department-wise) | PC 11 |
|---|---|
| Department | PC (Wolf) |
