  Understanding the speed limits for the propagation of magnons is of key
importance for the development of ultrafast spintronics and magnonics.
Recently, it was predicted that in 2D antiferromagnets, spin correlations can
propagate faster than the highest magnon velocity. Here we gain deeper
understanding of this supermagnonic effect based on time-dependent Schwinger
boson mean-field theory. We find that the supermagnonic effect is determined by
the competition between propagating magnons and a localized quasi-bound state,
which is tunable by lattice coordination and quantum spin value $S$, suggesting
a new scenario to enhance magnon propagation.
