Multiple quantum phases in artificial double-dot molecules

We study coupled semiconductor quantum dots theoretically through a generalized Hubbard approach, where intra- and inter-dot Coulomb correlation, as well as tunneling effects are described on the basis of realistic electron wavefunctions. We find that the ground-state configuration of vertically coupled double dots undergoes non-trivial quantum transitions as a function of the inter-dot distance d; at intermediate values of d we predict a new phase that should be observable in the addition spectra and in the magnetization changes. (C) 1999 Elsevier Science Ltd. All rights reserved.