  Antiferromagnetic magnons possess a distinctive feature absent in their
ferromagnetic counterparts: the presence of two distinct handedness modes, the
right-handed (RH) and left-handed (LH) precession modes. The magnon handedness
determines the sign of spin polarization carried by the propagating magnon,
which is indispensable for harnessing the diverse functionalities. However, the
control of coherently propagating magnon handedness in antiferromagnets has
remained elusive so far. Here we demonstrate the manipulation and electrical
readout of propagating magnon handedness in perpendicularly magnetized
synthetic antiferromagnets (SAF). We find that the antiferromagnetic magnon
handedness can be directly identified by measuring the inverse spin Hall effect
(ISHE) voltage, which arises from the spin pumping effect caused by the
propagating antiferromagnetic magnons in the SAF structure. The RH and LH modes
of the magnon can be distinguishable particularly when the SAF structure is
sandwiched by heavy metals with the same sign of spin Hall angle. Moreover, we
succeed in controlling the handedness of propagating antiferromagnetic magnons
by tuning the excitation microwave frequency. This work unveils promising
avenues for harnessing magnon unique properties in antiferromagnet-based
magnonic applications.
