Distinct Three-Level Spin–Orbit Control Associated with Electrically Controlled Band Swapping

We investigate the Rashba and Dressehaus spin–orbit (SO) couplings in an ordinary GaAs/AlGaAs asymmetric double well, which favors the electron occupancy of three subbands ν = 1, 2, 3. Resorting to an external gate, which adjusts the electron occupancy and the well symmetry, we demonstrate distinct three-level SO control of both Rashba (α_ν) and Dresselhaus (β_ν) intraband terms. Remarkably, as the gate varies, the first-subband SO parameters α ₁ and β ₁ comply with the usual linear behavior, while α ₂ (β ₂) and α ₃ (β ₃) respectively for the second and third subbands interchange the values, triggered by a gate controlled band swapping. This provides a pathway towards fascinating selective SO control in spintronic applications. Moreover, we observe that the interband Rashba (η_μν) and Dresselhaus (Γ_μν) terms also exhibit contrasting gate dependence. Our results should stimulate experiments probing SO couplings in multi-subband wells and adopting relevant SO features in future spintronic devices. (paper)