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DS: Fachverband Dünne Schichten

DS 11: 2D semiconductors and van der Waals heterostructures II (joint session HL/DS)

DS 11.1: Hauptvortrag

Montag, 16. März 2020, 15:00–15:30, POT 81

Resonantly hybridized excitons in moiré superlattices in van der Waals heterostructures — •Alexander Tartakovskii — Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK

Recent years have seen significant effort in exploration of monolayer semiconductors such as transition metal dichalcogenides (TMDs) MoS₂, WS₂, MoSe₂, WSe₂ etc. Atomically-thin layers of two-dimensional materials can be assembled in vertical stacks held together by relatively weak van der Waals forces, allowing for coupling between monolayer crystals with incommensurate lattices and arbitrary mutual rotation. The lattice constant difference and the mutual rotation angle present new degrees of freedom for the design of novel meta-materials.

A profound consequence of using these new degrees of freedom is the emergence of an overarching periodicity in the local atomic registry of the constituent crystal structures, known as a moiré superlattice. Here, we show that in semiconducting heterostructures built of incommensurate MoSe₂ and WS₂ monolayers, excitonic bands can hybridize, which results in the resonant enhancement of the moiré superlattice effects. MoSe₂ and WS₂ are specifically chosen for the near degeneracy of their conduction band edges to promote the hybridization of intra- and interlayer excitons. For MoSe₂/WS₂ heterostructures with almost aligned pairs of monolayer crystals, the resonant mixing of the electron states leads to amplified effects of the heterostructure’s geometrical moiré pattern on the dispersion of the hybridised excitons.