  An inhomogeneous magnetic exchange field at a superconductor/ferromagnet
interface converts spin-singlet Cooper pairs to a spin-aligned (i.e.
spin-polarized) triplet state. Although the decay envelope of such triplet
pairs within ferromagnetic materials is well studied, little is known about
their decay in non-magnetic metals and superconductors, and in particular in
the presence of spin-orbit coupling (SOC). Here we investigate devices in which
triplet supercurrents are injected into the s-wave superconductor Nb. In the
normal state of Nb, triplet supercurrents decay over a distance of 5 nm, which
is an order of magnitude smaller than the decay of spin singlet pairs due to
the SOC interacting with the spin associated with triplet pairs. In the
superconducting state of Nb, triplet supercurrents are not able to couple with
the singlet wavefunction and thus blocked by the absence of available
equilibrium states in the singlet gap. The results offer new insight into the
dynamics between s-wave singlet and s-wave triplet states.
