For what concerns the Rashba–Edelstein effect, the spin-split dispersion relation consists in two bands displaced along the k -axis due to a structural inversion asymmetry (SIA), accordingly to the Rashba effect (i.e., these bands show a linear splitting in k due to the spin-orbit coupling). This results in two Fermi countours, which are concentric at equilibrium, both displaying spin-momentum locking but with opposite helicity. If the system is driven in an out-of-equilibrium condition by injecting a charge current, the two disk displace one from the other and a net spin accumulation arises. This effect occurs, for instance, in a bidimensional Rashba gas. The Rashba splitting complicates the understanding and the visualization of the spin-to-charge conversion mechanism but the basic working principle of the Rashba–Edelstein effect is very similar to the one of the Edelstein effect.