Polarization and excitation power-dependent photoluminescence of magnetic/non-magnetic coupled quantum dots

The magneto-photoluminescence experiments have been performed on a coupled quantum dots (QDs) system composed of CdSe and CdMnSe QD double layers. The photoluminescence peaks from two QD layers forms a wide PL band due to the inhomogeneous broadening of QD ensemble in the coupled QD system. The intensity of the PL band undergoes significant change when a magnetic field is applied. Specifically, the QD system shows large difference in intensity between σ^- and σ⁺ circular polarizations, which results from the spin polarization of carriers in the presence of magnetic field. Interestingly, while the lower energy side of the PL band was dominated by the σ⁺ circular polarization, the higher energy side of the band was dominated by the σ^- circular polarization. Furthermore, the relative PL intensity at the low energy side of the band remarkably increases with decrease in excitation power for the σ⁺ circular polarization, while it showed no significant change for σ^- circular polarization. Such polarization and excitation power-dependent behaviors of PL intensity enable us to identify the relative potential profile of the magnetic/non-magnetic coupled QD systems.