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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 34: Two-dimensional Materials III (joint session HL/CPP)

CPP 34.9: 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.