Speaker
Description
Monolayers of semiconducting transition metal dichalcogenides (TMDs) build a new class of atomically thin two-dimensional materials. They exhibit a remarkably strong Coulomb interaction giving rise to the formation of tightly bound excitons. In addition to regular bright excitonic states, there is also a variety of dark states that cannot be accessed by light due to the required momentum-transfer or spin-flip.
To model the exciton physics in TMD monolayers, we apply a microscopic approach combining semiconductor Bloch equations with the Wannier equation providing access to time- and momentum-resolved optical response and the non-equilibrium dynamics in TMDCs. In this talk, we review our recent work focusing on:
(i) Uncovering the full exciton landscape including bright as well as momentum- and/or spin-forbidden dark excitonic states [1].
(ii) Revealing the microscopic origin of the excitonic lifetime including radiative and phonon-assisted non-radiative relaxation channels [2,3].
(iii) Providing a fully quantum mechanical description of formation, thermalization, and decay of bright and dark excitons and their impact on photoluminescence and pump-probe spectroscopy [4,5].
(iv) Demonstrating signatures of dark excitons, when probing the intra-excitonic 1s-2p transition shortly after excitation and after exciton thermalization [6].
(v) Activation of momentum-forbidden dark excitonic states via efficient coupling with molecules and suggesting a novel dark-exciton-based sensing mechanism for molecules [7].
[1] E. Malic, M. Selig, M. Feierabend, S. Brem, D. Christiansen, F. Wendler, A. Knorr,
G. Berghaeuser, Phys. Rev. Materials 2, 014002 (2018).
[2] M. Selig, 7. M. Selig, G. Berghaeuser, M. Richter, R. Bratschitsch, A. Knorr, and E. Malic, Nature Commun. 7, 13279 (2016).
[3] D. Christiansen, M. Selig, G. Berghaeuser, R. Schmidt, I. Niehues, R. Schneider, A. Arora, S. Michaelis de Vasconcellos, R. Bratschitsch, E. Malic, A. Knorr, Phys. Rev. Lett. 119, 187402 (2017).
[4] M. Selig G. Berghaeuser, M. Richter, R. Bratschitsch, A. Knorr, E. Malic, arXiv: 1703.03317.
[5] S. Brem, G. Berghaeuser, M. Selig, E. Malic, arXiv:1712.04808.
[6] G. Berghaeuser, P. Steinleitner, P. Merkl, R. Huber, A. Knorr, and E. Malic, arXiv: 1708.07725.
[7] M. Feierabend, G. Berghäuser, A. Knorr, E. Malic, accepted by Nature Commun. (2017).
