Coherent control of magnon radiative damping with local photon states

TL;DR

This paper demonstrates how local photon states in a cavity can be used to coherently control magnon radiative damping, enabling tunable photon emission and energy transfer in magnon-photon systems.

Contribution

It introduces a method to manipulate magnon radiation by tailoring the local density of photon states in a cavity, advancing control over magnon-photon interactions.

Findings

Magnon radiative damping is proportional to the local density of photon states.

Tuning photon polarization and magnitude modulates magnon emission.

Efficient photon emission from magnons achieved in a cavity-waveguide system.

Abstract

The collective excitation of ordered spins, known as spin waves or magnons, can in principle radiate by emitting travelling photons to an open system when decaying to the ground state. However, in contrast to the electric dipoles, magnetic dipoles contributed by magnons are more isolated from electromagnetic environment with negligible radiation in the vacuum, limiting their application in coherent communication by photons. Recently, strong interaction between cavity standing-wave photons and magnons has been reported, indicating the possible manipulation of magnon radiation via tailoring photon states. Here, with loading an yttrium iron garnet sphere in a one-dimensional circular waveguide cavity in the presence of both travelling and standing photon modes, we demonstrate an efficient photon emissions from magnon and a significant magnon radiative damping with radiation rate found to be proportional to the local density of states (LDOS) of photon. By modulating the LDOS including its magnitude and/or polarization, we can flexibly tune the photon emission and magnon radiative damping on demand. Our findings provide a general way in manipulating photon emission from magnon radiation for harnessing energy and angular momentum generation, transfer and storage modulated by magnon in the cavity and waveguide electrodynamics.