Gyrotropy Supported Wave Propagation in Antiferromagnets

Antiferromagnets, unlike conventional ferromagnets, can have all the diagonal terms distinct in the permeability tensor, giving rise to diverse topologies of isofrequency surfaces over the frequency spectrum. Interestingly, antiferromagnets have all the diagonal permeability terms as negative over a narrow frequency band. Our work shows the existence of a gyrotropy-supported propagating mode, even when all the permeability terms are negative. We investigate the photonic-spin profile of this gyrotropy-supported mode over the isofrequency surface. Further, we consider an antiferromagnet-filled waveguide and show an asymmetric photonic-spin profile with an asymmetric offset in the Poynting vector for forward and backward propagating modes.