Probing dark exciton navigation through a local strain landscape in a WSe<sub>2</sub> monolayer.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 35017506.
- Also identified by DOI 10.1038/s41467-021-27877-2 and PMC identifier 8752834.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
In WSe<sub>2</sub> monolayers, strain has been used to control the energy of excitons, induce funneling, and realize single-photon sources. Here, we developed a technique for probing the dynamics of free excitons in nanoscale strain landscapes in such monolayers. A nanosculpted tapered optical fiber is used to simultaneously generate strain and probe the near-field optical response of WSe<sub>2</sub> monolayers at 5 K. When the monolayer is pushed by the fiber, its lowest energy states shift by as much as 390 meV (>20% of the bandgap of a WSe<sub>2</sub> monolayer). Polarization and lifetime measurements of these red-shifting peaks indicate they originate from dark excitons. We conclude free dark excitons are funneled to high-strain regions during their long lifetime and are the principal participants in drift and diffusion at cryogenic temperatures. This insight supports proposals on the origin of single-photon sources in WSe<sub>2</sub> and demonstrates a route towards exciton traps for exciton condensation.