  The charge stability diagram for two coupled quantum dots containing up to
two electrons is computed in magnetic fields. One- and two-particle
Schroedinger equations are solved by exact diagonalization to obtain the
chemical potentials and exchange energy in these systems. By analyzing the
chemical potentials variation with external biases and magnetic fields, it is
possible to distinguish between the weak and strong inter-dot couplings. The
variation of the chemical potential curvatures and the double-triple point
separations in the stability diagrams confirms the inter-dot coupling decrease
with increasing magnetic fields. The computed exchange energies are also found
to be significantly smaller than the values estimated from the stability
diagram.
