Field-induced spin excitations in Rashba-Dresselhaus two-dimensional electron systems probed by surface acoustic waves

A spin-rotation symmetry in spin-orbit coupled two-dimensional electron systems gives rise to a long-lived spin excitation that is robust against short-range impurity scattering. The influence of a constant in-plane electric field on this persistent spin helix is studied. To probe the field-induced eigen-modes of the spin-charge coupled system, a surface acoustic wave is exploited that provides the wave-vector for resonant excitation. The approach takes advantage of methods worked out in the field of space-charge waves. Sharp resonances in the field dependence of the in-plane and out-of-plane magnetization are identified.