Anticorrelation between the splitting and polarization of the exciton fine structure in single self-assembled InAs/GaAs quantum dots

Abstract

We report on a systematic correlation between the fine-structure splitting and polarization anisotropy of excitons in InAs/GaAs quantum dots, but with an unexpected reversal in order of the polarization eigenaxes. Such an anticorrelation is explained by a large valence-band-mixing induced splitting due to the shape and strain anisotropies. The strength and phase of valence band mixing are also found to play an important role in the tuning of fine structure splitting using an in-plane magnetic field.

Polarization properties of excitonic qubits in single self-assembled quantum dots

“…It is not also clear if the correlations reported in Ref. 18 are observed on a large area or in a very precise region on the sample. Our experimental results were obtained over hundreds of dots on different areas on the sample surface.…”

“…Therefore, a large dispersion of values for the heavy to light-hole mixing parameters can be found in the literature. [13][14][15]18 Moreover, since morphological details and precise values for the different strain components can not be obtained at the same time for each studied QD by optical experiments, it is quite impossible to know precisely the origin of valence-band mixing.…”

“…In strain-free GaAs QDs grown by droplet epitaxy it has been shown that VBM exists due to the anisotropy of the confinement potential, 15 while in strained self-assembled InAs/GaAs QDs, VBM effects have been investigated in order to estimate the exciton spin relaxation time, 16 its influence on the exciton FSS, 17,18 or the hyperfine coupling. 19 To our knowledge, no experimental study includes both strain effects and confinement anisotropy in order to explain the observed results, which can be fully described by combining the Luttinger-Kohn and the Bir-Pikus Hamiltonians.…”

Light-hole exciton mixing and dynamics in Mn-doped quantum dots

“…Under strong tensile strain the anisotropic exchange interaction increases and one can switch the ground state of a QD from heavy hole to light hole [28]. For isotropic QD confinement potential the bright exciton splitting vanishes [30,31]. Moreover, for the QDs considered here the strain is assumed to be small and therefore the FSS is neglected.…”

Magnetic field control of the neutral and charged exciton fine structure in single quantum dashes emitting at 1.55 μm

“…Although the concept of reducing the FSS in inverted spin configuration structure by magnetic field was already utilized, 17 FSS crossing was reached for less than 30% of the dots, which indicates that post selection is a limiting factor. Suggestions that the heavy-hole lighthole mixing effect is responsible for a sign change 18 makes strongly elongated nanostructures very promising candidates, while a non-zero degree of linear polarization reflecting strong light-hole admixture 19,20 has been reported recently. 21 Therefore, our attention is focused on InAs/InGaAlAs/ InP quantum dashes (QDashes) elongated in [1][2][3][4][5][6][7][8][9][10] crystallographic direction.…”