Spin drag measurements were performed in a two-dimensional electron systemset close to the crossed spin helix regime and coupled by strong intersubbandscattering. In a sample with uncommon combination of long spin lifetime andhigh charge mobility, the drift transport allows us to determine the spin-orbitfield and the spin mobility anisotropies. We used a random walk model todescribe the system dynamics and found excellent agreement for the Rashba andDresselhaus couplings. The proposed two-subband system displays a large tuninglever arm for the Rashba constant with gate voltage, which provides a new pathtowards a spin transistor. Furthermore, the data shows large spin mobilitycontrolled by the spin-orbit constants setting the field along the directionperpendicular to the drift velocity. This work directly reveals the resistanceexperienced in the transport of a spin-polarized packet as a function of thestrength of anisotropic spin-orbit fields.
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