Broadband Nonreciprocity Enabled by Strong Coupling of Magnons and Microwave Photons

Abstract

Non-reciprocity of signal transmission enhances capacity of communication channels and protects transmission quality against possible signal instabilities, thus becoming an important component ensuring coherent information processing. However, non-reciprocal transmission requires breaking time-reversal symmetry (TRS) which poses challenges of both practical and fundamental character hindering the progress. Here we report a new scheme for achieving broadband non-reciprocity using a specially engineered hybrid microwave cavity. The TRS breaking is realized via strong coherent coupling between a selected chiral mode in the microwave cavity and a single collective spin excitation (magnon) in a ferromagnetic yttrium iron garnet (YIG) sphere. The non-reciprocity in transmission is observed spanning nearly a 0.5 GHz frequency band, which outperforms by two orders of magnitude the previously achieved bandwidths. Our findings suggest a promising direction for robust coherent information processing in a broad range of systems in both classical and quantum regimes.

Quantum Engineering With Hybrid Magnonic Systems and Materials (Invited Paper)

“…As a result, time reversal symmetry can be broken on a cavity supporting circularly polarized microwave resonances, which can further result in nonreciprocal transmission if the photon polarization is port-dependent. 197 In an alternative approach, time reversal symmetry can be broken using a linearly polarized λ/2 cavity. 198 Reversing the signal propagation direction changes the phase of the cavity field at the position of the YIG sphere, which in turn induces nonreciprocity in the cavity transmission.…”

Circulating cavity magnon polaritons

“…Analogous with structures that are coupled by optical resonators [17], metamaterials [18], and dielectric nanostructures [19,20], multiple magnets inside a cavity form new collective modes by the real or virtual exchange of cavity photons [10,21,22]. The polarization-momentum coupling of confined electromagnetic waves [23][24][25] can be employed to realize magnet-based broadband nonreciprocity and devices such as circulators [26,27] and a magnon accumulation in an open waveguide [28][29][30].…”

Advances in Magnetics Roadmap on Spin-Wave Computing

“…Moreover, specific properties of the resonator also affect the system dynamics. For instance, in hybrid magnon-microwave photon systems, the microwave polarization is a key parameter to be tuned to produce nonreciprocal behaviors [506].…”