Slow and highly confined plasmons observed in atomically thin TaS<sub>2</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 40593663.
- Also identified by DOI 10.1038/s41467-025-60814-1 and PMC identifier 12216657.
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Abstract
Extreme light confinement down to the atomic scale has been theoretically predicted for ultrathin, Ta-based transition metal dichalcogenides (TMDs). In this work, we report the observation of highly confined plasmons in 2H-TaS<sub>2</sub> monolayers and bilayers via momentum-resolved electron energy loss spectroscopy (q-EELS), with a resolution of 0.0056 Å<sup>-1</sup>. Momentum-dispersed two-dimensional (2D) plasmon resonances were found to exhibit a lateral confinement ratio up to 300 at large wave vectors of q = 0.15 Å<sup>-1</sup> and slow light behaviour with a group velocity ~10<sup>-4</sup>c. Moreover, we observed a transition from 2D to 3D Coulomb interaction in the high-momentum regime, equivalent to light confinement volumes of 1-2 nm<sup>3</sup>. Remarkably, the resonant modes do not enter the electron-hole continuum, potentially enabling even further enhanced optical field confinements for this material at cryogenic temperatures.