  Spin current is a central theme in spintronics, and its generation is a keen
issue. The spin-polarized current injection from the ferromagnet, spin battery,
and spin Hall effect have been used to generate spin current, but Ohmic
currents in the normal state are involved in all of these methods. On the other
hand, the spin and spin current manipulation by the supercurrent in
superconductors is a promising route for dissipationless spintronics. Here we
show theoretically that, in two-dimensional superconductors with Rashba
spin-orbit interaction, the generation of dissipationless bulk spin current by
charge supercurrent becomes highly efficient, exceeding that in normal states
in the dilute limit, i.e. when the chemical potential is close to the band
edge, although the spin density becomes small there. This result manifests the
possibility of creating new spintronic devices with long-range coherence.
