Probing intervalley coupling via exciton hybridization in a charge-tunable GaAs/AlAs quantum dot

We study a type-II GaAs/AlAs quantum dot system that enables intervalley coupling between electronic states in the Γ and Xz valleys, probed optically at the single-dot level. This structure intrinsically supports both direct and indirect excitons, with their spatial separation tunable via an external electric field. Stark shift spectroscopy reveals a clear double anticrossing in the neutral exciton line as a direct signature of intervalley coupling. Experimental observations, including measurements of static dipole moments and electron g factors, confirm electron confinement within the AlAs barrier and highlight the involvement of barrier-localized states. We further propose that these states may contribute to the formation of multicharged excitonic complexes. A simplified model allows us to estimate the interfacial coupling strength from the measured anticrossing amplitudes.