New type of “dark” states in the spectrum of radiative magnon polarons

The appearance of new types of bound (“dark”) states in the continuous spectrum of shear phonons of the radiation field of leaky magnon polarons in an acoustically open “easy-axis antiferromagnet–superconductor” sandwich structure can be determined by the relative orientation of the plane of incidence of a transverse elastic wave and the equilibrium antiferromagnetism vector in the interface plane between the media. The effect is based on the elastic dipole mechanism of the formation of magneto-acoustic birefringence with a change of the refraction cavity induced by the symmetric or antisymmetric Dzyaloshinskii interaction.