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<p>Monolayer (1L) transition metal dichalcogenides (TMDs) provide a unique opportunity to control the valley degree of freedom of optically excited charge carriers due to the spin-valley locking effect. However, a unified picture of competing intervalley coupling processes in 1L-TMDs is lacking. Here, we apply broadband helicity-resolved transient absorption to explore exciton valley polarization dynamics in 1L-WSe<sub>2</sub>. By combining experimental results with microscopic simulations, we dissect individual intervalley coupling mechanisms and reveal the crucial role of phonon-assisted scattering in the fast decay of the A exciton circular dichroism and the formation of the dichroism of opposite polarity for the B exciton. We further provide a consistent description of the valley depolarization driven by an intervalley-exchange-activating momentum-dark Dexter process and indicate the presence of efficient single electron spin-flip mechanisms. Our study advances understanding of exciton dynamics in TMDs.</p>

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Dissecting intervalley coupling mechanisms in monolayer transition metal dichalcogenides

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月31日

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  • Oleg Dogadov,
  • Henry Mittenzwey,
  • Micol Bertolotti,
  • Nicholas Olsen,
  • Thomas Deckert,
  • Chiara Trovatello,
  • Xiaoyang Zhu,
  • Daniele Brida,
  • Giulio Cerullo,
  • Andreas Knorr,
  • Stefano Dal Conte

摘要

Monolayer (1L) transition metal dichalcogenides (TMDs) provide a unique opportunity to control the valley degree of freedom of optically excited charge carriers due to the spin-valley locking effect. However, a unified picture of competing intervalley coupling processes in 1L-TMDs is lacking. Here, we apply broadband helicity-resolved transient absorption to explore exciton valley polarization dynamics in 1L-WSe2. By combining experimental results with microscopic simulations, we dissect individual intervalley coupling mechanisms and reveal the crucial role of phonon-assisted scattering in the fast decay of the A exciton circular dichroism and the formation of the dichroism of opposite polarity for the B exciton. We further provide a consistent description of the valley depolarization driven by an intervalley-exchange-activating momentum-dark Dexter process and indicate the presence of efficient single electron spin-flip mechanisms. Our study advances understanding of exciton dynamics in TMDs.