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1. Cavity magnonics

   https://doi.org/10.1016/j.physrep.2022.06.001  

   Zare Rameshti, Babak; Viola Kusminskiy, Silvia; Haigh, James A.; Usami, Koji; Lachance-Quirion, Dany; Nakamura, Yasunobu; Hu, Can-Ming; Tang, Hong X.; Bauer, Gerrit E.W.; Blanter, Yaroslav M. (September 2022, Physics Reports)

   Fulvio Parmigiani (Ed.)

   Cavity magnonics deals with the interaction of magnons — elementary excitations in magnetic materials — and confined electromagnetic fields. We introduce the basic physics and review the experimental and theoretical progress of this young field that is gearing up for integration in future quantum technologies. Much of its appeal is derived from the strong magnon–photon coupling and the easily-reached nonlinear regime in microwave cavities. The interaction of magnons with light as detected by Brillouin light scattering is enhanced in magnetic optical resonators, which can be employed to cool and heat magnons. The microwave cavity photon-mediated coupling of a magnon mode to a superconducting qubit enables measurements in the single magnon limit. 

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2. Electrical manipulation of dissipation in microwave photon–magnon hybrid system through the spin Hall effect

   https://doi.org/10.1063/5.0182270  

   Hou, Justin T; Chou, Chung-Tao; Han, Jiahao; Fan, Yabin; Liu, Luqiao (February 2024, Applied Physics Letters)

   Hybrid dynamic systems combine advantages from different subsystems for realizing information processing tasks in both classical and quantum domains. However, the lack of controlling knobs in tuning system parameters becomes a severe challenge in developing scalable, versatile hybrid systems for useful applications. Here, we report an on-chip microwave photon–magnon hybrid system where the dissipation rates and the coupling cooperativity can be electrically influenced by the spin Hall effect. Through magnon–photon coupling, the linewidths of the resonator photon mode and the hybridized magnon polariton modes are effectively changed by the spin injection into the magnetic wires from an applied direct current, which exhibit different trends in samples with low and high coupling strengths. Moreover, the linewidth modification by the spin Hall effect shows strong dependence on the detuning of the two subsystems, in contrast to the classical behavior of a standalone magnonic device. Our results point to a direction of realizing tunable, on-chip, scalable magnon-based hybrid dynamic systems, where spintronic effects provide useful control mechanisms. 

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3. Formation of binary magnon polaron in a two-dimensional artificial magneto-elastic crystal

   https://doi.org/10.1038/s41427-023-00499-4  

   Majumder, Sudip; Drobitch, J L; Bandyopadhyay, Supriyo; Barman, Anjan (December 2023, NPG Asia Materials)

   Abstract We observed strong tripartite magnon-phonon-magnon coupling in a two-dimensional periodic array of magnetostrictive nanomagnets deposited on a piezoelectric substrate, forming a 2D magnetoelastic “crystal”; the coupling occurred between two Kittel-type spin wave (magnon) modes and a (non-Kittel) magnetoelastic spin wave mode caused by a surface acoustic wave (SAW) (phonons). The strongest coupling occurred when the frequencies and wavevectors of the three modes matched, leading to perfect phase matching. We achieved this condition by carefully engineering the frequency of the SAW, the nanomagnet dimensions and the bias magnetic field that determined the frequencies of the two Kittel-type modes. The strong coupling (cooperativity factor exceeding unity) led to the formation of a new quasi-particle, called a binary magnon-polaron, accompanied by nearly complete (~100%) transfer of energy from the magnetoelastic mode to the two Kittel-type modes. This coupling phenomenon exhibited significant anisotropy since the array did not have rotational symmetry in space. The experimental observations were in good agreement with the theoretical simulations. 

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4. Ellipticity‐Controlled Exceptional Points and Cross‐Polarized Phase Singularities in Multi‐Layer Silicon Guided Mode Resonant Metasurfaces

   https://doi.org/10.1002/adom.202500731  

   Goldberg, Ben; Zhang, Shuang; Lawrence, Mark (July 2025, Advanced Optical Materials)

   Abstract Precise control over light polarization is critical for advancing technologies in telecommunications, quantum computing, and image sensing. However, existing methods for manipulating polarization around exceptional points (EPs) in non‐Hermitian systems have exclusively focused on circular polarization and work with reflected light. To address this limitation, a novel metasurface platform with high‐Q resonators is developed that enables tunable control of polarization exceptional points across arbitrary ellipticity for transmitted light. This design employs orthogonally polarized guided mode resonators in a two‐layer silicon metasurface, where careful tuning of the dipolar guided mode resonances (DGMRs) and layer spacing allows us to control the ellipticity of EPs. By leveraging high‐quality factor resonances, strong orthogonal mode coupling over distances up to a quarter wavelength is achieved. This platform exhibits omnipolarizer behavior and the corresponding phase singularity can imprint phase shifts from 0 to 2π with small perturbations in the geometry. This approach opens new possibilities for polarization control and programmable wavefront shaping, offering significant potential for next‐generation optical devices. 

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5. Miniature High-Coupling Lithium Niobate Thin Film Bulk Acoustic Wave Resonators at 10-30 GHz

   https://doi.org/10.1109/IMS40360.2025.11103794  

   Chulukhadze, Vakhtang; Wang, Yinan; Anderson, Ian; Kramer, Jack; Cho, Sinwoo; Lu, Ruochen (June 2025, IEEE)

   Thin film bulk acoustic wave resonators (FBARs) leveraging sputtered aluminum nitride (AlN) and scandium aluminum nitride (ScAlN) films, are a leading commercial solution for compact radio frequency (RF) filters in mobile devices. However, as 5G/6G bands extend beyond 6 GHz, achieving the required thinner piezoelectric film thicknesses below 500 nm presents a significant challenge to high-quality sputtering, resulting in a moderate quality factor (Q). Additionally, AlN/ScAlN platforms are limited by moderate electromechanical coupling (k2), restricting bandwidth. More recently, ultra-thin transferred single-crystal piezoelectric lithium niobate (LN) has enabled lateral field excited resonators (XBAR) at 10-30 GHz. While these devices boast a high Q and k2, they face challenges with low capacitance density, large footprint, and significant electromagnetic (EM) effects. On the other hand, thickness-field excited LN FBARs face challenges with bottom electrode integration. In this work, we implement a transferred LN on aluminum FBAR platform on sapphire wafers with an intermediate amorphous silicon layer without the need for a patterned bottom electrode. The resonators show first order symmetric mode (S1) at 10.5 GHz with a 3-dB series resonance Q of 38 and k2 of 14.1%, alongside third order symmetric mode (S3) at 27 GHz with a 3-dB series resonance Q of 22 and a high k2 of 11.3%. Further analysis shows that higher Q could be achieved by adjusting the low-loss piezoelectric to lossy metal volume ratio. 

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