Effect of illumination on the interplay between Dresselhaus and Rashba spin-orbit coupling in InAs quantum wells

Illumination of variable wavelength was used to study the dependence on the carrier concentration of the spin-orbit coupling and the semiconducting properties of a thin n-type InAs quantum well. Measurements of the sheet and Hall resistance were performed in variable magnetic field, field orientation, temperature, and under illumination with wavelengths of 400 nm up to 1300 nm. Beats in the Shubnikov-de Haas oscillations indicated the presence of strong spin-orbit coupling and the FFT of the oscillations points towards the presence of both Rashba and Dresselhaus spin-orbit interactions. Here we have used simulations to extract the dependence of the spin-orbit strengths on the carrier concentration. The simulations are based on the Hamiltonian of a 2D electron system with both types of spin-orbit interactions and subject to a perpendicular magnetic field. The results indicate that the Rashba coefficient decreases with increasing the carrier concentration, while the Dresselhaus coefficient remains mainly constant. These results are consistent with observations on similar materials where the carrier concentration was varied using applied gate voltage.