Spin orbit interaction and zitterbewegung in symmetric wells

Recently, we have introduced a novel inter-subband-induced spin-orbit (s-o) coupling (cond-mat/0607218) arising in symmetric wells with at least two subbands. This new s-o coupling gives rise to an usual zitterbewegung - i.e. the semiconductor analog to the relativistic trembling motion of electrons - with cycloidal motion without magnetic fields. Here we complement these findings by explicitly deriving expressions for the corresponding zitterbewegung in spin space.