Center-of-mass quantization of excitons in GaAs quantum-well wires

We have studied wide quantum-well-wire structures by polarization-dependent photoluminescence and photoluminescence excitation spectroscopy. We observe an up-to-threefold splitting of the lowest heavy-hole-excition resonance, which arises from a quantization of the excitonic center-of-mass motion perpendicular to the direction of the wires. The energy separation between these transitions depends on the active wire width Lₓ, which is significantly smaller than the geometrical wire width. Identifying the exciton wave vector Kₑₓⁿ with n{π}/Lₓ, we can reconstruct the exciton dispersion and find excellent agreement with theory if we use the k=0 heavy-hole mass.