Cavity-mediated coherent coupling of magnetic moments

Abstract

We demonstrate the long range strong coupling of magnetostatic modes in spatially separated ferromagnets mediated by a microwave frequency cavity. Two spheres of yttrium iron garnet are embedded in the cavity and their magnetostatic modes probed using a dispersive measurement technique. We find they are strongly coupled to each other even when detuned from the cavity modes. We investigate the dependence of the magnet-magnet coupling on the cavity detuning ∆, and find a 1/∆ dependence also characteristic of cavity-coupled superconducting qubits. Dark states of the coupled magnetostatic modes of the system are observed, and ascribed to mismatches between the symmetries of the modes and the drive field.

Level attraction and level repulsion of magnon coupled with a cavity anti-resonance

“…In addition to the fundamental uniform mode, coupling between photons and higher order non-uniform modes has also been studied, with coupling strength depending on the overlap between the magnon and caity modes [15,16]. For multiple YIG samples coupled to a microwave cavity mode [17,18], magnon dark modes have been observed, showing a way to couple distant magnetic systems. Currently, magnon-based hybrid systems have become a highly versatile platform for studying the coherent interactions between collective spin exciations and microwave photons, superconducting qubits [19], optical photons [20][21][22] and phonons [23,24].…”

Combined Brillouin light scattering and microwave absorption study of magnon-photon coupling in a split-ring resonator/YIG film system

“…[4][5][6][7] Furthermore, spin pumping in combination with the dc inverse spin Hall effect has been employed as a detection scheme for sensing the magnonic part of magnon-photon polaritons in magnetic thin film heterostructures, 6,8 which is effectively a down-conversion of the coupling to dc.…”

“…The prerequisite for information transfer on the quantum level is to realize a large coupling strength exceeding the loss rates of the subsytems, 4,7,9 here, the microwave resonator and the spin ensemble. Since the coupling rate is proportional to the square root of the number of participating spins 4,10 ferromagnets with a high spin density are ideal for the creation of strongly coupled, hybridized magnon-photon modes.…”

Microscopic origin of level attraction for a coupled magnon-photon system in a microwave cavity

“…In optomagnonics, cavity photons couple to magnetic excitations via the magnetooptical interactions, which allows characterization using a well-established optomechanical Hamiltonian [15,16], and, as a consequence, one should be able to observe optomechanical effects in magnetic systems [17]. Various phenomena have been proposed for coupled magnon-photon systems inside microwave cavities including Brillouin-scattering-induced transparency in whispering gallery resonators [18][19][20], collective dynamics of spin textures [21,22], and photon-mediated nonlocal interactions [23][24][25][26].…”