Nanocavity Clock Spectroscopy: Resolving Competing Exciton Dynamics in WSe<sub>2</sub>/MoSe<sub>2</sub> Heterobilayers.
basic_science · Level V
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- Record sourced from PubMed, PMID 33301334.
- Also identified by DOI 10.1021/acs.nanolett.0c03979.
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Abstract
Transition-metal dichalcogenide heterostructures are an emergent platform for novel many-body states from exciton condensates to nanolasers. However, their exciton dynamics are difficult to disentangle due to multiple competing processes with time scales varying over many orders of magnitude. Using a configurable nano-optical cavity based on a plasmonic scanning probe tip, the radiative (rad) and nonradiative (nrad) relaxation of intra- and interlayer excitons is controlled. Tuning their relative rates in a WSe<sub>2</sub>/MoSe<sub>2</sub> heterobilayer over 6 orders of magnitude in tip-enhanced photoluminescence spectroscopy reveals a cavity-induced crossover from nonradiative quenching to Purcell-enhanced radiation. Rate equation modeling with the interlayer charge transfer time as a reference clock allows for a comprehensive determination from the long interlayer exciton (IX) radiative lifetime τ<sub>IX</sub><sup>rad</sup> = (94 ± 27) ns to the 5 orders of magnitude faster competing nonradiative lifetime τ<sub>IX</sub><sup>nrad</sup> = (0.6 ± 0.2) ps. This approach of nanocavity clock spectroscopy is generally applicable to a wide range of excitonic systems with competing decay pathways.