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

Abstract

We studied the dependence on carrier density of the spin–orbit coupling (SOC) and of the semiconducting properties of a thin n-type InAs quantum well in the limit of high carrier density, when the second subband starts to populate. Measurements of sheet and Hall resistances were performed in a variable magnetic field, 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 fast Fourier transforms of the oscillations point toward the presence of both Rashba and Dresselhaus spin–orbit interactions. We used simulations to extract the carrier density dependence of the SOCs, based on the Hamiltonian of a single subband 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, with an accelerated decrease close to the transition to double occupancy. The Dresselhaus coefficient is not only smaller but also drops in the proximity of the transition, together with the carrier mobility and the Landau level broadening energy. This behavior is discussed in the context of phenomena associated with the onset of double occupancy and based on intersubband interactions.