Magnetoelectric Cavity Magnonics in Skyrmion Crystals

Recently, a strong coupling between magnons and microwave photons in a cavity has attracted much attention. Previous works have focused on the magnetic coupling between magnons and photons via the Zeeman effect. In comparison, multiferroic materials host electromagnons that can be excited by oscillating electric fields. Here, we present a theory of magnetoelectric magnon-photon coupling in cavities hosting noncentrosymmetric magnets. Analogously to nonreciprocal phenomena in multiferroics, the magnetoelectric coupling is time-reversal and inversion asymmetric. This asymmetry establishes a means for exceptional tunability of magnon-photon coupling, which can be switched on and off by reversing the magnetization direction.

Taking the multiferroic skyrmion-host Cu₂OSeO₃ as an example, we reveal the electrical activity of skyrmion eigenmodes and propose it for magnon-photon splitting of ``magnetically dark'' elliptic modes. Furthermore, we predict a cavity-induced magnon-magnon coupling between magnetoelectrically active skyrmion excitations. We discuss applications in quantum information processing by proposing protocols for all-electrical magnon-mediated photon quantum gates and a photon-mediated SPLIT operation of magnons. Our study shows magnetoelectric cavity magnonics as a novel platform for realizing a quantum-hybrid system.