Ultrafast Nanoscopy of High-Density Exciton Phases in WSe2
Journal article, 2022
The density-driven transition of an exciton gas into an electron-hole plasma remains a compelling question in condensed matter physics. In two-dimensional transition metal dichalcogenides, strongly bound excitons can undergo this phase change after transient injection of electron-hole pairs. Unfortunately, unavoidable nanoscale inhomogeneity in these materials has impeded quantitative investigation into this elusive transition. Here, we demonstrate how ultrafast polarization nanoscopy can capture the Mott transition through the density-dependent recombination dynamics of electron-hole pairs within a WSe2 homobilayer. For increasing carrier density, an initial monomolecular recombination of optically dark excitons transitions continuously into a bimolecular recombination of an unbound electron-hole plasma above 7 × 1012 cm-2. We resolve how the Mott transition modulates over nanometer length scales, directly evidencing the strong inhomogeneity in stacked monolayers. Our results demonstrate how ultrafast polarization nanoscopy could unveil the interplay of strong electronic correlations and interlayer coupling within a diverse range of stacked and twisted two-dimensional materials.
transition metal dichalcogenides
Mott transition
near-field microscopy
ultrafast dynamics
exciton
terahertz
Author
Thomas Siday
University of Regensburg
Fabian Sandner
University of Regensburg
Samuel Brem
Chalmers, Physics, Condensed Matter and Materials Theory
Philipps University Marburg
Martin Zizlsperger
University of Regensburg
Raul Perea Causin
Chalmers, Physics, Condensed Matter and Materials Theory
Felix Schiegl
University of Regensburg
Svenja Nerreter
University of Regensburg
Markus Plankl
University of Regensburg
Philipp Merkl
University of Regensburg
F. Mooshammer
Columbia University
University of Regensburg
Markus A. Huber
University of Regensburg
Ermin Malic
Philipps University Marburg
Chalmers, Physics, Condensed Matter and Materials Theory
R. Huber
University of Regensburg
Nano Letters
1530-6984 (ISSN) 1530-6992 (eISSN)
Vol. 22 6 2561-2568Graphene Core Project 3 (Graphene Flagship)
European Commission (EC) (EC/H2020/881603), 2020-04-01 -- 2023-03-31.
Subject Categories
Atom and Molecular Physics and Optics
Other Physics Topics
Condensed Matter Physics
DOI
10.1021/acs.nanolett.1c04741
PubMed
35157466