Numerical analysis of the spin-orbit coupling parameters in III-V quantum wells using 8-band Kane model and finite-difference method

TL;DR

This paper numerically analyzes spin-orbit coupling parameters in III-V quantum wells using an 8-band Kane model and finite-difference method, exploring effects of well parameters and electric fields on spin phenomena.

Contribution

It introduces a numerical approach combining the Kane model and finite-difference scheme to calculate spin-orbit coupling in quantum wells, revealing conditions for SU(2) symmetry and persistent spin helices.

Findings

Linear-in-momentum spin-orbit coupling vanishes at certain well widths and compositions.

Spin-orbit parameters can be equal at specific electric fields, enabling SU(2) symmetry.

Calculated spin-orbit coupling in the persistent spin helix regime as a function of structural parameters.

Abstract

By means the envelope function approximation, 8-band Kane model and a finite-difference scheme with the coordinate space discretization, we numerically performed calculations of the spin-orbit coupling parameters for 2D electron gas confined in both symmetric and asymmetric [0 0 1] quantum wells based on zinc-blende III-V semiconductors. Influence of the quantum well band parameters and width as well as the magnitude of the external electric field applied along the growth direction on the Dresselhaus and Rashba spin-orbit coupling parameters is investigated. It has been found that in the symmetric InGaAs/GaAs quantum wells linear-in-momentum spin-orbit coupling disappears for the third electron subband at certain values of well width and the indium content. It is also shown that in asymmetric InGaAs/GaAs structures the spin-orbit coupling parameters can be equal at a certain electric field that is the condition for the realization of the SU(2) spin symmetry and formation of persistent spin helices. Besides, we calculated the spin-orbit coupling in the persistent spin helix regime as a function of the well width, indium content and external field. The proposed approach for the calculation of the spin-orbit coupling parameters can be applied to other 2D structures with the spin-orbit coupling.