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 2561-2568

Graphene 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

More information

Latest update

3/7/2024 9