In this study, we explore the optical properties of quantum dots doped with a ${\mathrm{Ni}}^{2+}$ ion that interacts with a charged exciton. The carriers-${\mathrm{Ni}}^{2+}$ exchange interaction, which is dominated by coupling with holes, enables optical interaction with an individual localized spin. Systematic magneto-optical analysis reveals that the strain distribution at the ${\mathrm{Ni}}^{2+}$ site significantly influences its spin structure. In positively charged dots dominated by in-plane biaxial strain, the three spin states of ${\mathrm{Ni}}^{2+}$ ($S_z=0, S_z=\pm 1$) can be observed, and the magneto-optical spectra enable local strain anisotropy to be determined. However, in most of the dots, lower-symmetry strain mixes all the ${\mathrm{Ni}}^{2+}$ spin states, thereby increasing the number of observed optical transitions. In charged dots, we identify optical transitions that share a common excited state. They form a series of $\mathrm{\Lambda }$-level systems that can be individually addressed optically to determine the energy-level structure. Magneto-optical measurements demonstrate that the hole-${\mathrm{Ni}}^{2+}$ exchange interaction is antiferromagnetic and considerably stronger than the electron-${\mathrm{Ni}}^{2+}$ interaction. A spin-effective model that incorporates local strain orientation can successfully reproduce key experimental results. Furthermore, we demonstrate that low-symmetry terms in the hole-${\mathrm{Ni}}^{2+}$ exchange interaction must be considered to accurately describe the emission spectra details in a magnetic field.

Close

PrevNext

View figure in article

• Magneto-optics
• Optical & microwave phenomena
• Magnetic semiconductors
• Nanostructures
• Semiconductors
• Photoluminescence