Abstract
A magnon, the collective excitation of ordered spins, can spontaneously radiate a travelling photon to an open system when decaying to the ground state. However, in contrast to electric dipoles, magnetic dipoles by magnons are more isolated from the environment, limiting their radiation and coherent communication with photons. The recent progresses in strongly coupled magnon-photon system have stimulated the manipulation of magnon radiation via tailoring the photon states. Here, by loading an yttrium iron garnet sphere in a one-dimensional waveguide cavity supporting both the travelling and standing photon modes, we demonstrate a significant magnon radiative damping that is proportional to the local density of photon states (LDOS). By modulating the magnitude and/or polarization of LDOS, we can flexibly tune the photon emission and magnon radiative damping. Our findings provide a way to manipulate photon emission from magnon radiation, which could help harness angular momentum generation, transfer, and storage in magnonics.
Highlights
A magnon, the collective excitation of ordered spins, can spontaneously radiate a travelling photon to an open system when decaying to the ground state
A magnon is an elementary excitation of magnetic structure that is used as an information carrier in magnonics and magnon spintronics[1,2,3,4], because it carries polarization or “spins” since the magnetization precesses anticlockwise around the equilibrium state[1,2,3,4]
We find that the Magnon radiation controlled by local density of photon states (LDOS) polarization
Summary
A magnon, the collective excitation of ordered spins, can spontaneously radiate a travelling photon to an open system when decaying to the ground state. Very recently, pioneering works have combined the best features of cavity photons and the long-lifetime magnon in yttrium iron garnet (YIG)[12,13], demonstrating the cavity-magnon-polariton dynamics[14,15,16,17,18,19] Such highcooperativity hybrid dynamics stimulate the ideas of coherent information processing with magnons. The standing-wave component causes a coherent exchange between magnons and photons and induces a splitting gap in the dispersion, while the superposed travelling-wave component plays the key role of transferring radiated spin information to an open system. A relative suppression of the radiative damping at the cavity resonance compared with that at the detuned frequency is observed This phenomenon seems to be different from the conventional Purcell effect[29,35,36] in the conventional confined cavity, but could be understood by considering open-system photon mode structures. Due to the linearity nature of our work, we anticipate that our method offers a general approach to other prototype photonic systems or on-chip integrated devices for advancing the manipulation and delivery of radiated spin information
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