  Spin manipulation in coupled quantum dots is of interest for quantum
information applications. Control of the exchange interaction between electrons
and holes via an applied electric field may provide a promising technique for
such spin control. Polarization dependent photoluminescence (PL) spectra were
used to investigate the spin dependent interactions in coupled quantum dot
systems and by varying an electric field, the ground state hole energy levels
are brought into resonance, resulting in the formation of molecular orbitals
observed as anticrossings between the direct and indirect transitions in the
spectra. The indirect and direct transitions of the neutral exciton demonstrate
high and low circular polarization memory respectively due to variation in the
exchange interaction. The ratio between the polarization values as a function
of electric field, and the barrier height was measured. These results indicate
a possible method of tuning between indirect and direct configurations to
control the degree of exchange interaction.
