Resonant spin polarization and spin current in a two-dimensional electron gas

We study the spin polarization and its associated spin-Hall current due to electric-dipole-induced spin resonance in disordered two-dimensional electron systems. We show that the disorder-induced damping of the resonant spin polarization can be strongly reduced by an optimal field configuration that exploits the interference between the Rashba and Dresselhaus spin-orbit interactions. This leads to a striking enhancement of the spin susceptibility while the spin-Hall current vanishes at the same time. We give an interpretation of the spin current in geometrical terms which are associated with the trajectories the polarization describes in spin space.

Figure 1

(Color online) (a) Momentum-dependent magnetic fields induced by Rashba (black arrows) and Dresselhaus SOI [red (gray) arrows] ${\mathbf{\Omega }}_R\left(\mathbf{p}\right)=\alpha (p_y,-p_x)$ and ${\mathbf{\Omega }}_D\left(\mathbf{p}\right)=\beta (p_x,-p_y)$, respectively. Inset: The sum ${\mathbf{\Omega }}_R+{\mathbf{\Omega }}_D$ for equal strength of the SOI $(\alpha =\beta )$ is shown. The interference of the two types of SOI leads to a suppression or enhancement of the spin splitting in certain crystallographic directions. (b) Polar plot of the resonance susceptibility ${\overline{\chi }}^{\mathrm{res}}$ (in arbitrary units) as a function of $\theta$ for $\beta =\alpha ∕2$ and ${\omega }_L\tau =1$ (black, solid curve), ${\omega }_L\tau =2$ (red, dotted), and ${\omega }_L\tau =3$ (blue, dashed). The configuration of the external magnetic and electric fields ${\mathbf{B}}_0$ and ${\mathbf{E}}_0$ is shown. For ${\mathbf{B}}_0\Vert {\mathbf{E}}_0\Vert \left[110\right]$ both SOI contributions add constructively in the direction perpendicular to ${\mathbf{B}}_0$, leading to an enlarged Rabi field.