Berlin 2018 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 8: 2D materials (joint session HL/DS)
DS 8.3: Vortrag
Montag, 12. März 2018, 15:30–15:45, EW 201
Dielectric Engineering of Intra-excitonic Correlations in a van der Waals Heterostructure — •Philipp Steinleitner1, Philipp Merkl1, Alexander Graf1, Philipp Nagler1, Christian Schüller1, Tobias Korn1, Rupert Huber1, Samuel Brem2, Malte Selig3, Gunnar Berghäuser2, and Ermin Malic2 — 1Department of Physics, University of Regensburg, Regensburg, Germany — 2Department of Physics, Chalmers University of Technology, Gothenburg, Sweden — 3Department of Theoretical Physics, Technical University of Berlin, Berlin, Germany
Atomically thin transition metal dichalcogenide monolayers promise novel optoelectronic applications due to their direct bandgap in the optical range. Reduced Coulomb screening, in combination with the two-dimensionality, stabilizes excitons, even at room temperature. Due to the extreme confinement perpendicular to the plane of the material, excitons are particularly sensitive to the local surrounding environment. Thus, capping the monolayer with a dielectric material allows one to non-invasively change their hydrogen-like structure. Here we report how an insulating hexagonal boron nitride cover layer influences the intra-excitonic 1s-2p transition. Using time resolved pump/THz probe techniques, we trace both optically bright and dark exciton states and are able to extract quantitative information about transition energies and linewidths. We find that the cover layer redshifts the 1s-2p transition and leads to a decrease of its linewidth. Using microscopic modelling, we show that our experimental data also support the formation of dark excitons from an initially bright population.