  The spatial separation of electron spins followed by the control of their
individual spin dynamics has recently emerged as an essential ingredient in
many proposals for spin-based technologies because it would enable both of the
two spin species to be simultaneously utilized, distinct from most of the
current spintronic studies and technologies wherein only one spin species could
be handled at a time. Here we demonstrate that the spatial spin splitting of a
coherent beam of electrons can be achieved and controlled using the interplay
between an external magnetic field and Rashba spin-orbit interaction in
semiconductor nanostructures. The technique of transverse magnetic focusing is
used to detect this spin separation. More notably, our ability to engineer the
spin-orbit interactions enables us to simultaneously manipulate and probe the
coherent spin dynamics of both spin species and hence their correlation, which
could open a route towards spintronics and spin-based quantum information
processing.
