Optical properties of single quantum dots in high magnetic field

Abstract

The photoluminescence of quantum dots is studied in a high magnetic field regime where the cyclotron frequency is comparable to the confinement energy. Applying a magnetic field perpendicular to the lateral potential plane lifts the shell degeneracy and magneto-photoluminescence spectroscopy therefore provides a probe to investigate the energy shell structure of quantum dots. By isolating a single quantum dot, the inhomogeneous broadening from a distribution of dot sizes and compositions is eliminated and the fine structure of the spectrum is revealed. The orbital splitting of angular momentum states is shown to follow the Fock-Darwin scheme. However, it is also apparent that each angular momentum branch consists of two distinct lines whose magnetic field evolution cannot be explained by a simple Zeeman spin splitting. The dependence of line splitting on orbital state can be described by the addition of spin-orbit coupling to the Fock-Darwin model. Accordingly, a quantitative measurement of the spin-orbit coupling strength in self-assembled quantum dots is obtained for the first time.