Lecture by Prof. Ursula Wurstbauer

Light matter interaction in tunable 2D materials and artificial van der Waals solids

Atomically thin two-dimensional layered materials receive great interest because of their unique properties. Particularly, monolayers of semiconducting transition metal dichalcogenides (SC-TMDs), such as MoS2, excel due to their strong light-matter interaction that is dominated by exciton phenomena [1]. Key to the integration of SC-TDM and related artificial van der Waals solids into circuitries is the possibility to tune and engineer their properties on demand and on-chip e.g. by defects, dielectric environment or doping [2-5]. 
We apply inelastic light scattering together with emission and absorption to study the manifold coupling mechanism in van der Waal hetero- and hybrid structures. Moreover, interlayer excitons (IX) in vdW hetero-bilayers are intriguing systems to explore classical and quantum phases of interacting bosonic ensembles. We observe multiplet IX emission lines for MoSe2/WSe2 and MoS2/WS2 hetero-bilayers that are interpreted in terms of multi-valley excitons [6,7]. Our results provide fundamental insights into long-lived interlayer states in van der Waals heterostructures with possible bosonic many-body interactions. 

We acknowledge support by the Deutsche Forschungsgemeinschaft (DFG) via excellence cluster Nanosystems Initiative Munich (NIM), e-conversion as well as DFG project WU 637/4-1.

[1] U. Wurstbauer, et al. J. Phys. D: Appl. Phys. 50, 173001 (2017).
[2] S. Diefenbach, et al., J. Phys. Chem. C, 122 (17), 9663–9670 (2018).
[3] J. Klein, et al., 2D Materials 5, 011007 (2018), J. Klein et al., arXiv:1901.01042 (2019).
[4] B. Miller, et al., Appl. Phys. Lett. 106, 122103 (2015).
[5] B. Miller et al. Nature Commun. 10, 807 (2019).
[6] B. Miller, et al., Nano Lett. 17(9), 5229–5237 (2017).
[7] J. Kiemle et al. arXiv:1901.01042 (2019).

Ursula Wurstbauer is from Institute of Physics, University of Münster, Germany