Multimode Cavity Magnonics System Models Coupling Phase Effects

Researchers of the IMT Atlantique, kwan-tek and Quantum Technologies and Dark Matter Labs of University of Western Australia, have uncovered how coupling-phase interference governs the behavior of multimode cavity magnonics systems, providing new insight into the interaction between microwave photons and magnons. Using a four-post re-entrant microwave cavity coupled to Yttrium Iron Garnet (YIG) spheres, the team demonstrated that the relative arrangement of coupling phases strongly influences the system’s response. Their findings show that coupling-phase engineering is a fundamental design principle for controlling complex cavity magnonic devices.

To understand these interactions, the researchers developed an input-output model that incorporates both internal and external coupling phases, allowing theoretical predictions to closely match experimental microwave transmission measurements. This comprehensive framework explains how interference between coupling phases shapes the behavior of multimode cavity magnonics systems and reveals effects that conventional models do not capture.

One of the study’s key findings is the emergence of a positionally dependent uncoupled mode caused by interference between internal cavity photon-magnon coupling phases. Rather than arising from weak coupling or imperfections, this uncoupled mode is an intrinsic consequence of phase interference within the cavity, highlighting the important role that coupling phases play in determining the system’s dynamics.

The researchers also experimentally observed strong nonreciprocity at antiresonance frequencies. Their analysis shows that this behavior results from the interplay between the odd-parity cavity photon-probe coupling phase and the internal photon-magnon coupling phases. The agreement between theoretical modeling, numerical simulations, and experimental measurements provides compelling evidence for the underlying interference mechanism.

The four-post re-entrant cavity geometry enables precise control over coupling phases, making it an effective platform for investigating multimode magnonic interactions. While coupling strength has traditionally received most attention in cavity magnonics, the study demonstrates that coupling phases can be equally important, particularly in systems containing multiple interacting modes.

By establishing coupling-phase interference as a key factor governing multimode cavity magnonics, the research provides a new framework for engineering microwave-magnon devices. These findings could support the development of advanced hybrid quantum systems, nonreciprocal microwave components, and information-processing technologies that rely on precise control of light-matter interactions.