arXiv subjects

Yongzhang Shi

Publications and source records attributed to Yongzhang Shi.

4 recordsLinked to original sources

arXiv2026

Revealing Magnon-Photon Coupling in Ultrathin Magnetic Films Using the Derivative-Divide Method

Magnon-photon coupling in planar cavities provides a promising platform for integrated cavity magnonics devices. However, its characterization becomes challenging in ultrathin magnetic films because their weak magnetic response can be obscured by the much stronger microwave background. Here, we employ the derivative-divide method to extract the field-dependent magnetic response from transmission measurements of split-ring resonators. The method reveals clear magn-photon anticrossings that are hardly discernible in conventional transmission spectra and enables quantitative extraction of the coupling strength. We resolve coupling in yttrium iron garnet films down to 60 nm and extend the approach to conductive CoFeB films down to 5 nm. Our results demonstrate a practical method for characterizing magno-photon coupling in ultrathin magnetic films, providing an experimental route toward cavity magnonics systems based on ultrathin magnetic films.

physics.app-ph↗

arXiv2025

Simultaneous nonreciprocal and ultra-strong coupling in cavity magnonics

We demonstrate the simultaneous realization of nonreciprocal coupling and ultra-strong coupling in cavity magnonics. By replacing a copper cylinder with a yttrium iron garnet cylinder within the photonic crystal, we achieve an ultra-strong coupling strength of 1.18 GHz and a coupling efficiency of 10.9%. Nonreciprocal microwave transmission emerges within the photonic bandgap, due to the breaking of time-reversal symmetry through the gyromagnetic and Faraday effects. This work establishes a foundation for advanced nonreciprocal devices in hybrid cavity magnonic systems, with promising applications in quantum information processing and microwave isolation.

physics.app-ph↗

arXiv2024

Nonreciprocal singularities dominated by the dissipative photon-magnon coupling in non-Hermitian systems

We investigated the magnon-photon coupling in an open cavity magnonic system, which leads to two different nonreciprocal singularities dominated by the dissipative coupling. One type of singularity is the exceptional point, which is just on the exceptional surface in parameter space. The other type of singularity is the bound state in the continuum discovered in the level-attraction-like coupling, which is above the exceptional surface. In experiment, we realized the two different singularities with nonreciprocity and selectivity in an open cavity magnonic system with suitable dissipation rating. Our results can be understood well with the pseudo-Hermitian theory of magnon-polariton system.

cond-mat.mes-hall↗

arXiv2021

Nonreciprocal Multi-mode and Indirect Couplings in Cavity Magnonics

We investigate the magnon-photon couplings by employing a small magnet within an irregular resonant cavity, which leads to a desirable nonreciprocity with a big isolation ratio. Moreover, the higher-order couplings between the spin wave modes with the polarized photon modes also exhibit the nonreciprocity. These couplings between polarized photon and spin waves could be regarded as an indirect multi-modes coupling between the ferromagnetic resonance (FMR) mode and spin wave mode magnons mediated by the cavity mode photons. We also derive a coupling matrix to predict the characteristics of this kind of indirect coupling. The existence of the indirect couplings broaden the field range of the nonreciprocity of the system. The achieved nonreciprocal multi-mode magnon-photon couplings in a single system offer a feasible method to improve the signal transmission quality.

physics.app-ph↗