M.-A. Dupertuis

Electronic model for self-assembled hybrid organic/perovskite semiconductors: Reverse band edge electronic states ordering and spin-orbit coupling

Based on density functional theory, the electronic and optical properties of hybrid organic/perovskite crystals are thoroughly investigated. We consider the monocrystalline 4F-PEPI as material model and demonstrate that the optical process is governed by three active Bloch states at the Gamma point of the reduced Brillouin zone with a reverse ordering compared to tetrahedrally bonded semiconductors. Giant spin-orbit coupling effects and optical activities are subsequently inferred from symmetry analysis.

Symmetries and optical transitions of hexagonal quantum dots in GaAs/AlGaAs nanowires

We investigate the properties of electronic states and optical transitions in hexagonal GaAs quantum dots within Al0.3Ga0.7As nanowires, grown in axial direction [111]. Such dots are particularly interesting due to their high degree of symmetry. A streamlined postsymmetrization technique based on class operators (PTCO) is developed which enables one to benefit from the insight brought by the maximal symmetrization and reduction of fields (MSRF) approach reported by Dalessi et al. [Phys. Rev. B 81, 125106 (2010)], after having solved the Schrodinger equation. Definite advantages of the PTCO are that it does not require modification of existing code for the calculation of the electronic structure, and that it allows to numerically test for elevated symmetries. We show in the frame of a four-band k . p model that despite the fact that the D-6h symmetry of the nanostructure is broken at the microscopic level by the underlying zinc-blende crystal structure, the effect is quite small. Most of the particularities of the electronic states and their optical emission can be understood by symmetry elevation to D-6h and the presence of approximate azimuthal and radial quantum numbers.

Symmetry Elevation and Symmetry Breaking: Keys to Describe and Explain Excitonic Complexes in Semiconductor Quantum Dots

The results of a group theoretical analysis of the excitonic fine structure are presented and compared with spectroscopic data on single quantum dots. The spectral features reveal the signatures of a symmetry higher than the crystal symmetry (C-3v). A consistent picture of the fine structure patterns for various exciton complexes is obtained with group theory and the concepts of symmetry elevation and symmetry breaking.