  We investigate the spin-Nernst effect in time-reversal invariant topological
superconductors, and show that it provides a smoking-gun evidence for helical
Cooper pairs. The spin-Nernst effect stems from asymmetric, in spin space,
scattering of quasiparticles at nonmagnetic impurities, and generates a
transverse spin current by the temperature gradient. Both the sign and the
magnitude of the effect sensitively depend on the scattering phase shift at
impurity sites. Therefore the spin-Nernst effect is uniquely suitable for
identifying time-reversal invariant topological superconducting orders.
