Strongly confined 2D parabolic quantum dot: Biexciton or Quadron?

Excitonic systems localized in a single InAs/GaAs parabolic quantum dot are studied theoretically using an unrestricted Hartree-Fock method. The binding energies of excitons, conventional biexcitons and quadrons - four particles system of two electrons and two holes, in the ground state have been obtained as functions of magnetic field and confinement potential. It is found that for strong confinement, while the binding energy of biexciton is negative, the binding energy of quadron is positive, suggesting the strong lateral confinement of the parabolic quantum dot supports the formation of a quadron rather than a biexciton.