Theory of magnetic response in two-dimensional giant Rashba system

The magnetic susceptibility of a disordered two-dimensional system with strong Rashba spin-orbit interaction is calculated in a self-consistent Born approximation. In an ideal system, the response exhibits a delta-function singularity toward the diamagnetic direction at the energy where the band crossing takes place in an inner Weyl band. It is essentially paramagnetic below that energy except for the system with a certain value of $g$ factor, while it becomes the same as that in a system free from the spin-orbit interaction above the energy. It turns out that effects of disorder are not sensitive to kinds of scatterers such as short- and long-range. Explicit numerical results are presented in the case of dominant charged-impurity scattering. The delta-function susceptibility is broadened by disorder but remains appreciable in the case of strong disorder.