High-lying excitons and tuneable excitonic quantum optics in stacked van-der-Waals semiconductors

Principal investigator

Sebastian Bange, Institut für Experimentelle und Angewandte Physik, Universität Regensburg [webpage]

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Abstract

We study the linear and nonlinear optical properties of unconventional, high-lying excitonic states in TMDC homo- and heterobilayers. In contrast to such species in monolayers, these can form spatially indirect, longer-living species with significant interlayer electronic hybridization and static dipole moments, controllable by both electric fields and electrostatic doping. In comparison to band-edge excitons, the high-lying excitons are significantly more sensitive to interlayer coupling, as exhibited by their high sensitivity to interlayer twist. Since they are separated in energy from typical near-gap defect states, they are prime candidates to investigate the influence on the upper conduction bands of a periodic moiré potential arising in twisted layers of van-der-Waals crystals.

TMDC multilayer systems are studied primarily through linear and nonlinear optical spectroscopy including harmonic generation, four-wave mixing and difference-frequency generation. Excitonic properties are tuned by the Stark effect through out-of-plane electric fields and electrostatic doping.