Polarization-dependent shift in excitonic Zeeman splitting of self-assembled ${\mathrm{In}}_{0.75}{\mathrm{Al}}_{0.25}\mathrm{As}∕{\mathrm{Al}}_{0.3}{\mathrm{Ga}}_{0.7}\mathrm{As}$ quantum dots

We report optical spectroscopic results of a single self-assembled ${\mathrm{In}}_{0.75}{\mathrm{Al}}_{0.25}\mathrm{As}∕{\mathrm{Al}}_{0.3}{\mathrm{Ga}}_{0.7}\mathrm{As}$ quantum dot. The polarization-dependent shift of the Zeeman splitting in a single InAlAs quantum dot (QD) has been observed. The induced Overhauser field is estimated to be $\sim 0.16\mathrm{T}$ in this InAlAs QD and the magnitude is shown to be controllable by the degree of circular polarization of excitation light.

Figure 1

(a) Ensemble PL spectra and single QD emissions (inset) from InAlAs QDs. (b) TEM image of a mesa structure.

Figure 2

(a) Photoluminescence spectra from the lowest exciton states of two different InAlAs QDs recorded at different magnetic fields. The spectra are normalized by the magnitude of the exciton emission around 1.5818 eV. (b) Magnetic-field dependence of the energy splitting of two exciton lines in InAlAs QDs shown in (a). Solid squares (for higher energy exciton) and circles (for lower energy exciton) are experimental data and the line is the fitting result using the forms obtained by diagonalizing the exciton fine-structure Hamiltonian.

Figure 3

(a) Excitonic emission energies for ${\sigma }_{+}$ excitation. $\mathrm{In}\mid B\mid ⩽1.5\mathrm{T}$, where the splitting is not clear, the ${\sigma }_{+}$ emissions (dotted lines) and ${\sigma }_{-}$ emissions (solid lines) were detected separately by using a quarter-wave plate and a linear polarizer. (b) Absolute values of the splitting energy are plotted for ${\sigma }_{+}$ excitation (open circles) and ${\sigma }_{-}$ excitation (black circles). The lines are the fitting curves by Eq. (1), and including Eq. (3), for ${\sigma }_{-}$ (solid) and ${\sigma }_{+}$ (dotted) excitations, respectively.

Figure 4

Energy splitting $\Delta E$ at 5 T is plotted as a function of the angle $\theta$ of the quarter-wave plate used to change the excitation polarization. The polarization of the excitation light is illustrated above the top axis. In the figure, $\Delta E_0$ is the Zeeman splitting for linearly polarized excitation that is indicated by the dotted line. The solid curve is a fitting line.