A generic model with unconventional Rashba bands and giant spin galvanic effect

In two-dimensional system, Rashba spin-orbit coupling can lift spin degeneracy and gives the opposite spin chirality of two split Fermi circles from two Rashba bands. Here, we propose a generic model which can produce unconventional Rashba bands. In such a case, the two Fermi circles from two bands have the same spin chirality. When various interactions are taken into account, many unique physics can emerge in case of unconventional Rashba bands in comparison with in case of conventional Rashba bands. For instance, we study the spin galvanic effect by considering two cases with potential impurity scattering and magnetic impurity scattering, respectively. In both cases, we find the efficiency of spin galvanic effect is strongly enhanced in unconventional Rashba bands in comparison with conventional Rashba bands. More intriguingly, we find the effeiciency of conventional Rashba bands is insensitive to potential or magnetic impurity scattering. However, such efficiency of uncoventional Rashba bands can be further enhanced by the magnetic impurity scattering in comparison with the potential impurity scattering. Thus, the unconventional Rashba bands can give giant spin galvanic effect. These results show that this model is useful to explore abnormal physics in the systems with unconventional Rashba bands.