Exciton dissociation and interdot transport in CdSe quantum-dot molecules

One of the most important parameters that determine the transport properties of a quantum dot array is the exciton dissociation energy, i.e., the energy $\Delta E$ required to dissociate an exciton into an electron and a hole localized in different dots. We show that a pseudopotential calculation for a dot molecule, coupled with a basic configuration interaction calculation of the exciton energy levels, provides directly the exciton dissociation energy, including the effects of wave function overlap, screened Coulomb attraction between the electron and the hole in different dots, and polarization effects. We find that $\Delta E$ decreases as the interdot distance decreases and as the dielectric constant of the medium increases.