  We investigate the impact of spin torque and spin pumping on the surface
magnon polariton dispersion in a antiferromagnetic insulator-semiconductor
heterostructure. In the bilayer system, the surface magnon polaritons
conventionally couple to the plasma-oscillations in the semiconductor via
electromagnetic fields. Additionally, magnons in the antiferromagnetic
insulator layer may interact with the semiconductor layer via spin torques and
their reciprocal phenomena of spin pumping. Due to the spin-to-charge
conversion from the spin Hall and inverse spin Hall effects in the
semiconductor layer with a strong spin-orbit coupling, this can couple the
magnons to the plasmons in the semiconductor layer. Our research reveals that
modifications in the mode frequency and the hybridization gap induced by these
phenomena depend on the thickness of the antiferromagnetic layer. In thick
layers, the spin-pumping contribution to the frequency shift and damping is
inversely proportional to the wavelength, while in thin layers it is inversely
proportional to the thickness. Furthermore, hybridization of the surface magnon
polariton and dispersive magnons in the antiferromagnet is shown to depend on
both the thickness and wavelength of the modes.
