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Electronic structures of (In,Ga)As/GaAs quantum dot molecules made of dots with dissimilar sizes

Using single-particle pseudopotential and many-particle configuration interaction methods, we compare various physical quantities of (In,Ga)As/GaAs quantum dot molecules (QDMs) made of dissimilar dots (heteropolar QDMs) with QDMs made of identical dots (homopolar QDMs). The calculations show that the electronic structures of hetero-QDMs and homo-QDMs differ significantly at large inter-dot distance. In particular (i) Unlike those of homo-QDMs, the single-particle molecular orbitals of hetero-QDMs convert to dot localized orbitals at large inter-dot distance. (ii) Consequently, in a hetero-QMD the bonding-antibonding splitting of molecular orbitals at large inter-dot distance is significantly larger than the electron hopping energy whereas for homo-QDM, the bonding-antibonding splitting is very similar to the hopping energy. (iii) The asymmetry of the QDM increases significantly the double occupation for the two-electron ground states, and therefore affects the degree of entanglement of the two electrons.