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HL: Fachverband Halbleiterphysik
HL 27: Two-dimensional Materials III (joint session HL/CPP)
HL 27.9: Vortrag
Mittwoch, 3. April 2019, 11:45–12:00, H36
Internal structure and ultrafast dynamics of interlayer excitons in van der Waals heterostructures — •Philipp Merkl1, Philipp Steinleitner1, Fabian Mooshammer1, Kai-Qiang Lin1, Philipp Nagler1, Johannes Holler1, Christian Schüller1, John M. Lupton1, Tobias Korn1, Simon Ovesen2, Samuel Brem2, Ermin Malic2 und Rupert Huber1 — 1Department of Physics, University of Regensburg, D-93040 Regensburg, Germany — 2Department of Physics, Chalmers University of Technology, SE-41258 Göteborg, Sweden
In heterostructures of transition metal dichalcogenides, electrons and holes residing in adjacent monolayers can bind into spatially indirect excitons. Even though these interlayer bound pairs have attracted tremendous interest owing to their strong promise for novel optoelectronics and valleytronics, their binding energies have not been directly measured. Here we introduce a direct ultrafast access to Coulomb correlations acting between monolayers. For the prototypical case of WSe2/WS2 hetero-bilayers, phase-locked mid-infrared pulses allow us to measure the binding energy of interlayer excitons of 118 meV by revealing a novel 1s-2p resonance, well explained by a fully quantum mechanical model. Furthermore, we trace how an exciton gas photogenerated in the WSe2 layer directly transforms into interlayer excitons, without a strong intermediate phase of unbound electron-hole pairs. Depending on the stacking angle, intra- and interlayer species coexist on picosecond scales and relax into quantum confined states in moiré-induced nanodots.