Valley Zeeman Splitting-Enhanced Spin-Forbidden Dark Exciton Formation in Magnetically V‑Doped WSe₂ Monolayer and WSe₂/MoSe₂ Heterostructure

Although their formation mechanism in monolayer MoS₂ has been theoretically revealed, time-reversal symmetry intrinsically protects valley degeneracy, imposing a fundamental limit on the formation efficiency. However, effective strategies to overcome this limitation remain unclear.

Here, the photoexcitation and relaxation dynamics in the WSe₂ monolayer and WSe₂/MoSe₂ heterostructure are investigated through nonadiabatic molecular dynamics combined with light–matter interaction and the GW plus real-time Bethe–Salpeter equation. We discover that although many-body interactions, including electron–phonon coupling, electron–hole Coulomb and exchange interactions, and spin–orbit interaction, synergistically drive spin-forbidden dark exciton formation, inherent valley degeneracy restricts the formation efficiency to ∼50%.