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 \nu=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 (\alpha_\nu) and Dresselhaus (\beta_\nu) intraband terms. Remarkably, as the gate varies, the first-subband SO parameters \alpha_1 and \beta_1 comply with the usual linear behavior, while \alpha_2 (\beta_2) and \alpha_3 (\beta_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 (\eta_\mu\nu) and Dresselhaus (\varGamma_\mu\nu) 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.