Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 53: 2D Materials II: Transition Metal Dichalcogenides
O 53.6: Vortrag
Mittwoch, 3. April 2019, 11:45–12:00, H16
Spatial extent of the excited exciton states in WS2 monolayers from diamagnetic shifts — •Jonas Zipfel1, Johannes Holler1, Anatolie A. Mitioglu2, Mairana V. Ballotin2, Philipp Nagler1, Andreas V. Stier3, Takashi Taniguchi4, Kenji Watanabe4, Scott A. Crooker3, Peter C. M. Christianen2, Tobias Korn1, and Alexey Chernikov1 — 1Department of Physics, University of Regensburg D-93053, Germany — 2High Filed Magnet Laboratory (HFML -EMFL), Radboud University, 6525 ED Nijmegen, The Netherlands — 3National High Magnetic Field Laboratory, Los Alamos, New Mexcio 87545, USA — 4National Institute for Materials Science, Tsukuba, Ibaraki 305-004, Japan
Owing to strong Coulomb interactions, the properties of monolayer TMDCs are governed by the formation of tightly bound electron-hole pairs, with binding energies as high as 0.5 eV. This motivates questions of the appropriate description of these exciton states and in particular, their spatial extent. We use magneto-optical reflectance spectroscopy in fields up to 29T to detect energy shifts of exciton ground and excited state resonances in encapsulated WS2 monolayers. These characteristic shifts arise both due to the valley Zeeman and diamagnetic effects. We find similar Zeeman shifts for ground and excited states. An analysis of the diamagnetic shifts allows us to draw direct conclusions on the spatial extent of the exciton states. Exciton radii of about 2nm for the ground and, more importantly, up to 5-8nm for the excited state are obtained, further confirming the applicability of a Wannier-Mott like description of excitons in monolayer semiconductors.