Controlling the spin-orbit amplitude in a non-flat quantum well

Using the inverse-scattering theory, we adjust the wave functions of a quantum well so that electrons occupying two lowest subbands conserve their spin projection, while the electrons occupying the third subband experience Rashba spin-orbit interaction. Shifting the Fermi level in the well with an external gate, one can drastically change the strength of the spin-orbit interaction felt by electrons. Such system can work as a spin-orbit trigger which has two states: (i) when the spin projection $s_z$ is a constant and (ii) when the spin precesses due to the spin-orbit interaction.