Second bound state of negatively charged excitons in quantum dots

By using the method of few-body physics, the binding energy spectra of the second bound state of a negatively charged exciton X− in a GaAs quantum dot with a parabolic confinement have been calculated as a function of the electron-to-hole mass ratio and of the dot radius. In the case of L=1 and S12=1 our calculation predicts the existence of a second bound state of X− in QDs.