Manifestation of the Coupling Phase in Microwave Cavity Magnonics

The interaction between microwave photons and magnons is well understood and originates from the Zeeman coupling between spins and a magnetic field. Interestingly, the magnon-photon interaction is accompanied by a phase factor, which can usually be neglected. However, under the rotating wave approx-imation, if two magnon modes simultaneously couple with two cavity resonances, this phase cannot be ignored as it changes the physics of the system. We consider two such systems, each differing by the sign of one of the magnon-photon coupling strengths. This simple difference, originating from the vari-ous coupling phases in the system, is shown to preserve, or destroy, two potential applications of hybrid photon-magnon systems, namely dark-mode memories and cavity-mediated coupling. The observable consequences of the coupling phase in this system is akin to the manifestation of a discrete Pancharatnam-Berry phase, which may be useful for quantum information processing and the creation of nonreciprocal devices using proper cavity engineering.

Automated summary

The interaction between microwave photons and magnons is well described by the Zeeman coupling between spins and a magnetic field. However, under the rotating wave approximation, the phase factor accompanying the magnon-photon interaction becomes important when two magnon modes simultaneously couple with two cavity resonances. This phase difference, resulting from the various coupling phases in the system, can either preserve or destroy two potential applications of hybrid photon-magnon systems, dark-mode memories and cavity-mediated coupling. The observable consequences of the coupling phase in this system resemble a discrete Pancharatnam-Berry phase, which has potential applications in quantum information processing and nonreciprocal devices via cavity engineering.