Fig. 5. Theoretical model of localization.

a Representation of the fully delocalized center-of-mass exciton state $∣\mathbf{K}=0⟩$ in (top) real space and (bottom) reciprocal space. The pictures highlight that this state is fully delocalized in real space with a position-independent probability and fully localized at K = 0 in reciprocal space. The inset top-left depict (filled blue area) the exciton center-of-mass (de)localization and (dashed line) the electron-hole separation. The inset bottom-right represents the optical transition from the nanoplatelet ground state to the $∣\mathbf{K}=0⟩$ state, where the thickness of the arrow is a measure of the oscillator strength. b–c The progressive localization of the exciton center of mass in real space leads to a progressive delocalization of the state in reciprocal space. As the contribution of the $∣\mathbf{K}=0⟩$ state is reduced, the oscillator strength of the optical transition from the ground state to a localized exciton goes down