ABSTRACT
In order to accurately evaluate the exchange energy in realistic double quantum dots (QD) systems accounting for the quantum device environement, we employ a hybrid multiscale method in which the confinement potential is obtained from the self-consistent solution of the three-dimensional Poisson equation with device boundary conditions. In magnetic fields, the exchange energy becomes negative at about 1.5 T in the single dot regime, and the singlet-triplet transition gradually shifts to ~1 T when the voltage is made more positive and the QD decouple. This decrease can be explained by the rising influence of the Coulomb interaction compared to the single-particle effects. We have calculated the exchange energy in the two-electron system confined in a realistic double QD structure by the numerically exact diagonalization of the corresponding Schrodinger equation within the full quantum device environment.
