Fig. 3

Valley polarization of interlayer excitons. a Top: polarization-resolved PL spectra for the AA-stacked hBL using σ⁺ excitation at 1.96 eV. Bottom: the degree of circular polarization P_C. b Polarization-resolved PL spectra near the X^I peak using σ⁺ excitation at 1.64 eV (MoSe₂) in AA- (top) and AB- (bottom) stacked hBLs. c The atomic registries and the phases associated with the interlayer transition dipoles in AA and AB stacking. A distinct phase factor \(e^{i{\mathrm{\tau }}{\mathbf{K}} \cdot {\mathbf{r}}_n}\) is associated with each interlayer transition dipoles between the nearest Mo and W atoms in different layers. d Left: the formation of \({\mathrm{X}}_{ + + }^{\mathrm{I}}\) state in AA-stacked hBLs using σ⁺ excitations at +K valleys in MoSe₂ and WSe₂ layers. Right: the formation of the interlayer dark state in AB-stacked hBLs using σ⁺ excitations at both MoSe₂ and WSe₂ layers. Red and blue lines are WSe₂ and MoSe₂ bands, respectively. Solid and dotted lines represent bands with different spins. Vertical arrows indicate optical excitations. Gray arrows represent spin-conserving interlayer transfer to the lowest energy band