Two-particle calculation of excitonic effects in semiconductor nanocrystals

We present a novel method for calculating the excitonic properties of nanometer-sized semiconductor structures. The method uses a time-dependent checkerboard propagation technique within the tight-binding approximation, and includes the electron-hole Coulomb interaction in the zeroth order Hamiltonian. We illustrate the method with two-particle calculations of exciton energies in CdSe and Si nanocrystals. The results of the two-particle calculations are compared with calculations which treat the Coulomb interaction perturbatively, and with measured absorption energies.