  Generation and detection of spinful Cooper pairs in conventional
superconductors has been intensely pursued by designing increasingly complex
magnet-superconductor hybrids. Here, we demonstrate theoretically that magnons
with nonzero wavenumbers universally induce a cloud of spinful triplet Cooper
pairs around them in an adjacent conventional superconductor. The resulting
composite quasiparticle, termed magnon-cooparon, consists of a spin flip in the
magnet screened by a cloud of the spinful superfluid condensate. Thus, it
inherits a large effective mass, which can be measured experimentally.
Furthermore, we demonstrate that two magnetic wires deposited on a
superconductor serve as a controllable magnonic directional coupler mediated by
the nonlocal and composite nature of magnon-cooparons. Our analysis predicts a
quasiparticle that enables generation, control, and use of spinful triplet
Cooper pairs in the simplest magnet-superconductor heterostructures.
