Biexciton and Quadron in Self-assembled Quantum Dots

We theoretically study biexcitons and quadrons in quantum dots with parabolic confinement and give a complete comparison between the two excitations. The calculation of quadron and biexciton binding energies as functions of electron-to-hole confinement potentials and mass ratios, using unrestricted Hartree-Fock method, shows the essential differences between biexciton and quadron. The crossover between the negative and positive binding energies is indicated. Besides, the effect of external magnetic field on the quadron and biexciton binding energies has also been investigated. In addition, the crossing between anti-binding and binding of both excited quadron and biexciton states at a certain range of the electron-to-hole oscillator length ratios has been found.