Regensburg 2022 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 24: 2D Materials 5 (joint session HL/CPP/DS)
CPP 24.2: Talk
Wednesday, September 7, 2022, 09:45–10:00, H36
Ultrafast nanoscopy of a Mott transition in twisted bilayer WSe2 — •Svenja Nerreter1, Thomas Siday1, Fabian Sandner1, Samuel Brem2,3, Martin Zizlsperger1, Felix Schiegl1, Raul Perea-Causin3, Markus Plankl1, Philipp Merkl1, Fabian Mooshammer1,4, Markus A. Huber1, Ermin Malic2,3, and Rupert Huber1 — 1Department of Physics and Regensburg Center for Ultrafast Nanoscopy, University of Regensburg, 93040 Regensburg — 2Department of Physics, Philipps-Universität Marburg, 35032 Marburg, Germany — 3Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden — 4Department of Physics, Columbia University, New York, NY 10027, USA
The density-driven transition of an exciton gas into a Fermi liquid of unbound electron-hole pairs has formed a compelling testing ground of many-body physics. Layered transition metal dichalcogenides feature advantageous conditions, yet nanoscale inhomogeneities have complicated quantitative studies of this elusive transition. Here, we use ultrafast polarization nanoscopy to trace optically bright and dark electronhole pairs during an exciton Mott transition in a twisted homobilayer of WSe2. At elevated densities, initially monomolecular recombination dynamics of optically dark excitons continuously evolve into the bimolecular recombination of unbound electron-hole pairs. We directly reveal how the Mott transition varies over nanometer length scales, evidencing strong spatial disorder in stacked monolayers and demonstrating the capabilities of our technique to resolve the local interplay of strong electronic correlations.