Light-Matter Interaction at Interfaces of Quantum Materials

Summary

This project aims at gaining microscopic insights into light-matter interaction at interfaces of quantum materials focusing in particular on Moiré-exciton features. Stacking monolayers of transition metal dichalcogenides (TMDCs) into a heterostructure provides atomically sharp and nearly defect-free interfaces. Adding a finite twist angle between the adjacent layers gives rise to artificial Moiré superlattices with a tunable periodicity. This constitutes an unprecedented possibility of engineering the optoelectronic landscape of quantum materials and designing versatile heterointerfaces for light-matter interaction.

Using sophisticated many-particle models based on density-matrix formalism, we will provide microscopic access to time-, momentum- and space-resolved dynamics of excitons, phonons, and photons at the interface of TMDC-based heterostructures. We will consider the full exciton landscape in TMDCs including bright and dark intra- and interlayer excitons. We will take into account hybridisation effects and trapping of excitons in spatially dependent Moiré potentials. Exploiting the twist angle as a new degree of freedom, we will investigate the possibility of tailoring exciton optics and spatiotemporal dynamics at TMDC/TMDC and TMDC/graphene interfaces as well as interfaces between TMDCs and organic semiconductors (OSCs). In particular, we will study on microscopic footing the interplay of optical excitation, formation of interlayer excitons, exciton relaxation cascade along the Moiré minibands, population and indirect emission of momentum-dark intervalley excitons, and finally exciton diffusion and localisation in the Moiré-trapping potentials.

The proposed project contributes to the core aim of the SFB to microscopically understand and externally control many-particle processes at interfaces of quantum materials. The planned studies will be conducted in close collaboration with the partner projects in the SFB.

Project-related publications

1. R. Wallauer, R. Perea-Causin, L. Münster, S. Zajusch, S. Brem, J. Güdde, K. Tanimura, K.-Q. Lin, R. Huber, E. Malic, U. Höfer
   Momentum-resolved observation of exciton formation dynamics in monolayer WS₂
   Nano Lett. (2021).
2. Brem, C. Linderälv, P. Erhart, E. Malic
   Tunable phases of moire excitons in van der Waals heterostructures
   Nano Lett. 20, 8534 (2020).
3. P. Merkl, F. Mooshammer, S. Brem, A. Girnghuber, K. Lin, L. Weigl, M. Liebich, C. Yong, R. Gillen, J. Maultzsch, J. Lupton, E. Malic, R. Huber
   Twist-tailoring Coulomb correlations in van der Waals homobilayers
   Nature Commun. 11, 2167 (2020).