Mapping the magnon–magnon hybrid state onto the Bloch sphere

Abstract

We investigate magnon–magnon hybrid states using a non-Hermitian Hamiltonian and the concept of magnon hybridization. By comparing our model with micromagnetic simulations conducted on a synthetic antiferromagnet with strong magnon–magnon coupling, the two-level model reproduces not only the resonance frequencies and linewidths but also the phases and amplitudes of the magnon eigenmode. The coherent coupling between magnons results in both the anticrossing of the energy spectra and the mixing of the linewidths. Specially, it forms a two-level system and makes the eigenmode of the hybrid state as a linear combination of the pure acoustic and optic modes. After that, we map the magnon–magnon hybrid state, including the magnon state of exceptional point, onto a Bloch sphere, which enhances the ability to manipulate hybrid magnons for coherent information processing.