  We theoretically investigate correlated electron-hole states in vertically
coupled quantum dots. Employing a prototypical double-dot confinement and a
configuration-interaction description for the electron-hole states, it is shown
that the few-particle ground state undergoes transitions between different
quantum states as a function of the interdot distance, resulting in unexpected
spatial correlations among carriers and in electron-hole localization. Such
transitions provide a direct manifestations of inter- and intradot
correlations, which can be directly monitored in experiments.
