Tunable cooperativity in coupled spin-cavity systems

The authors experimentally demonstrate the tunable coupling between microwave photons and the magnetic excitations (magnons) in the topologically nontrivial skyrmion lattice phase of the helimagnet Cu${}_{2}$OSeO${}_{3}$. They exploit distinct microwave excitation geometry of the skyrmion lattice breathing mode to achieve a wide tunability of the effective magnon-photon coupling rate by small variations of the external magnetic field. The authors succeed in realizing high cooperativity for the dispersive magnon-photon coupling in the skyrmion lattice phase.