Symmetry of $k\cdot p$ Hamiltonian in pyramidal InAs/GaAs quantum dots: Application to the calculation of electronic structure

TL;DR

This paper presents a symmetry-based method for calculating the electronic structure of pyramidal InAs/GaAs quantum dots, accounting for strain and magnetic effects, revealing novel miniband behaviors.

Contribution

It introduces a symmetry-adapted basis for 8-band $k ext{·}p$ Hamiltonian calculations in quantum dots, enabling detailed analysis of electronic states under various conditions.

Findings

Ground hole state symmetry changes with dot spacing

Magnetic field influences miniband splitting and overlap

Strain affects miniband effective mass and state symmetry

Abstract

A method for the calculation of the electronic structure of pyramidal self-assembled InAs/GaAs quantum dots is presented. The method is based on exploiting the exact $\bar{C}_{4}$ symmetry of the 8-band $k\cdot p$ Hamiltonian with the strain taken into account via the continuum mechanical model. The operators representing symmetry group elements were represented in the plane wave basis and the group projectors were used to find the symmetry adapted basis in which the corresponding Hamiltonian matrix is block diagonal with four blocks of approximately equal size. The quantum number of total quasi-angular momentum is introduced and the states are classified according to its value. Selection rules for interaction with electromagnetic field in the dipole approximation are derived. The method was applied to calculate electron and hole quasibound states in a periodic array of vertically stacked pyramidal self-assembled InAs/GaAs quantum dots for different values of the distance between the dots and external axial magnetic field. As the distance between the dots in an array is varied, an interesting effect of simultaneous change of ground hole state symmetry, type and the sign of miniband effective mass is predicted. This effect is explained in terms of the change of biaxial strain. It is also found that the magnetic field splitting of Kramer's double degenerate states is most prominent for the first and second excited state in the conduction band and that the magnetic field can both separate otherwise overlapping minibands and concatenate otherwise nonoverlapping minibands.