Brightening of dark trions in monolayer WS$_2$ via localization of surface plasmons
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| Format: | Preprint |
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2025
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| _version_ | 1866918303440568320 |
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| author | Raha, Sreyan Bhattacharya, Tara Shankar Bose, Indrani Singha, Achintya |
| author_facet | Raha, Sreyan Bhattacharya, Tara Shankar Bose, Indrani Singha, Achintya |
| contents | Among all excitonic complexes in transition-metal dichalcogenides (TMDs), dark and semi-dark trions are poised to play a stellar role in future quantum technologies due to their long lifetimes, about two orders of magnitude greater than those of their bright counterparts. In monolayer (ML) tungsten disulphide (WS$_2$), accessing these states via a suitable brightening mechanism remains challenging, specially, at elevated temperatures. Here, we demonstrate the brightening of dark trions from ML WS$_2$ over the temperature range, 83 K-115 K, enabled by localized surface plasmon modes in a disordered gold substrate. The resulting photoluminescence (PL) spectrum reveals a distinct spectral doublet with the twin peaks of semi-dark and bright trion states, separated by $\sim$ 45 meV. The origin of the semi-dark trion state lies in intervalley electron-electron scatterings, while its visibility in the PL spectrum is made possible by the enhanced out-of-plane electromagnetic field associated with plasmon localization. We also report on the negative degree of circular polarization in ML WS$_2$ at the energy of the semi-dark trion state. Our results establish a scalable plasmonic route to access valley-polarized semi-dark trions, opening new opportunities for quantum and valleytronic applications. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_10856 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Brightening of dark trions in monolayer WS$_2$ via localization of surface plasmons Raha, Sreyan Bhattacharya, Tara Shankar Bose, Indrani Singha, Achintya Mesoscale and Nanoscale Physics Among all excitonic complexes in transition-metal dichalcogenides (TMDs), dark and semi-dark trions are poised to play a stellar role in future quantum technologies due to their long lifetimes, about two orders of magnitude greater than those of their bright counterparts. In monolayer (ML) tungsten disulphide (WS$_2$), accessing these states via a suitable brightening mechanism remains challenging, specially, at elevated temperatures. Here, we demonstrate the brightening of dark trions from ML WS$_2$ over the temperature range, 83 K-115 K, enabled by localized surface plasmon modes in a disordered gold substrate. The resulting photoluminescence (PL) spectrum reveals a distinct spectral doublet with the twin peaks of semi-dark and bright trion states, separated by $\sim$ 45 meV. The origin of the semi-dark trion state lies in intervalley electron-electron scatterings, while its visibility in the PL spectrum is made possible by the enhanced out-of-plane electromagnetic field associated with plasmon localization. We also report on the negative degree of circular polarization in ML WS$_2$ at the energy of the semi-dark trion state. Our results establish a scalable plasmonic route to access valley-polarized semi-dark trions, opening new opportunities for quantum and valleytronic applications. |
| title | Brightening of dark trions in monolayer WS$_2$ via localization of surface plasmons |
| topic | Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2512.10856 |