Electrically Tunable Valley Dynamics in Twisted WSe2/WSe2 Bilayers

The twist degree of freedom provides a powerful new tool for engineering the electrical and optical properties of van der Waals heterostructures. Here, we show that the twist angle can be used to control the spin-valley properties of transition metal dichalcogenide bilayers by changing the momentum alignment of the valleys in the two layers. Specifically, we observe that the interlayer excitons in twisted WSe₂/WSe₂ bilayers exhibit a high (>60 % ) degree of circular polarization (DOCP) and long valley lifetimes (>40 ns ) at zero electric and magnetic fields. The valley lifetime can be tuned by more than 3 orders of magnitude via electrostatic doping, enabling switching of the DOCP from ∼80 % in the n -doped regime to <5 % in the p -doped regime. These results open up new avenues for tunable chiral light-matter interactions, enabling novel device schemes that exploit the valley degree of freedom.