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HL: Fachverband Halbleiterphysik

HL 31: Focus Session: Young Semiconductor Forum Poster

HL 31.7: Poster

Mittwoch, 19. März 2025, 12:15–13:00, H13

Hybridized excitons in 2D van der Waals materials — •Andreas Stier — Walter Schottky Institut und TUM School of Natural Sciences, TU München, Garching, Deutschland

I will review our recent progress on magneto optical spectroscopy of atomically thin materials in magnetic fields up to 91 T with an emphasis on the spin-valley physics of neutral and charged excitons.

In monolayer (ML) semiconductors, magneto-absorption spectroscopy revealed the diamagnetic shifts of the exciton Rydberg states, which allowed the first direct experimental measure of the reduced mass and binding energy. Surprisingly, investigating the photoluminescence, we observe the emergence of a new excitonic peak, which we discuss in the framework of the theoretically predicted linear dispersing exciton branch originating from intervalley exchange interactions.

For heterostructures (HS) of a 2D semiconductor with graphene, we find a new multi-step proximity effect due to band folding in the HS, where we show that the spin-valley physics can be used to quantify interlayer hybridization. In HS from ML MoSe2 and the layered antiferromagnetic (AFM) semiconductor CrSBr, we show the formation of new exciton states depending on the twist angle. These excitons exhibit clear signatures of proximity coupling to the magnetic state of the AFM layer, such as hysteretic response to in- and out of plane B fields. We discuss these results in the framework of Ising-type spin-orbit proximity coupling.

Keywords: van der Waals materials; heterostructures; excitons; CrSBr; graphene