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We present high-quality numerical calculations of the exciton center-of-mass dispersion for GaAs/AlGaAs quantum wells of widths in the range 2 − 20 nm. The k · p -coupling of the heavy-and light-hole bands is fully taken into account. An optimized center-of-mass transformation enhances numerical convergence. We derive an easy-to-use semi-analytical expression for the exciton groundstate mass from an ansatz for the exciton wavefunction at finite momentum. It is checked against the numerical results and found to give very good results. We also show multiband calculations of the exciton groundstate dispersion using a finite-differences scheme in real space, which can be applied to rather general heterostructures.

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We present for the rst time numerical calculations of the center-of-mass (c.o.m.)dispersion of an exciton in a quantum well using a nite-dierences method. The coupling of heavy-and light-hole bands is accounted for ink Áp -theory, while the conduction band dispersion is assumed parabolic. We motivate a suitable choice of the c.o.m. coordinate system, which increases remarkably the numerical accuracy for nite c.o.m. wavevector. The desired eigenvalues and eigenfunctions of the involved huge matrices are calculated with modern iterative sparse matrix solvers. Results are shown for the example case of a GaAs=Ga:7Al:3As <100> quantum well.

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