Bright and Dark Excitons in 2D Semiconductors and Heterostructures

PC Department Online Seminar
Date: Nov 9, 2020
Time: 11:00 AM (Local Time Germany)
Speaker: Alexander Högele
Fakultät für Physik, Munich Quantum Center, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität, München

Van der Waals crystals of transition metal dichalcogenide (TMD) semiconductors have evolved as an increasingly significant material platform for condensed matter research. They can be routinely exfoliated down to the monolayer limit or assembled into rationally designed vertical heterostructures. In response to optical excitations, both semiconductor systems host strongly bound excitons in various configurations of spin and valley degrees of freedom.

We use optical spectroscopy at cryogenic temperatures and in the presence of external magnetic fields to study characteristic signatures of various spin-valley polarized exciton species in TMD monolayers [1,2], homobilayers [2,3] and heterostructures [4,5], and identify their role in the elementary optical responses in absorption and emission.

[1] J. Lindlau et al., Identifying optical signatures of momentum-dark excitons in transition metal dichalcogenide monolayers, arXiv:1710.00988 (2017).
[2] J. Förste et al., Exciton g-factors in monolayer and bilayer WSe2 from experiment and theory, Nat. Commun. 11, 4539 (2020).
[3] J. Lindlau et al., The role of momentum-dark excitons in the elementary optical response of bilayer WSe2, Nat. Commun. 9, 2586 (2018).
[4] M. Förg et al., Cavity-control of interlayer excitons in van der Waals heterostructures, Nat. Commun. 10, 3697 (2019).
[5] M. Förg et al., Moiré excitons in MoSe2-WSe2 heterobilayers and heterotrilayers, arXiv:2006.09105 (2020).

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