Robust magnon-photon coupling in a planar-geometry hybrid of inverted split-ring resonator and YIG film

Abstract

We experimentally demonstrate strongly enhanced coupling between excited magnons in an Yttrium Iron Garnet (YIG) film and microwave photons in an inverted pattern of split-ring resonator (noted as ISRR). The anti-crossing effects of the ISRR’s photon mode and the YIG’s magnon modes were found from |S21|-versus-frequency measurements for different strengths and directions of externally applied magnetic fields. The spin-number-normalized coupling strength (i.e. single spin-photon coupling) was determined to 0.194 Hz ( = 90 MHz) at 3.7 GHz frequency. Furthermore, we found that additional fine features in the anti-crossing region originate from the excitation of different spin-wave modes (such as the magnetostatic surface and the backward-volume magnetostatic spin-waves) rather than the Kittel-type mode. These spin-wave modes, as coupled with the ISRR mode, modify the anti-crossing effect as well as their coupling strength. An equivalent circuit model very accurately reproduced the observed anti-crossing effect and its coupling strength variation with the magnetic field direction in the planar-geometry ISRR/YIG hybrid system. This work paves the way for the design of new types of high-gain magnon-photon coupling systems in planar geometry.

Strong Coupling between Magnons and Microwave Photons in On-Chip Ferromagnet-Superconductor Thin-Film Devices

“…It comes from the small mode volume V c ∼ 0.0051 mm 3 for the coplanar resonator and indicates the significance of having a localized and concentrated photon mode volume to reach a strong coupling strength. It is worthwhile to note a few different planar resonator designs such as split-ring [17,39,40] and lumped-element resonators [41,42]. The former allows an optimal filling of thin-film magnetic materials in the resonator, with g/2π close to 1 GHz; the latter has the highest g 0 by further reducing the mode volume.…”

Expanding the Lorentz concept in magnetism

“…In recent years there has been growing interest into incorporating thin magnetic films (100 μm-100 nm) into metamolecules [1][2][3][4] and magnonic devices [5,6]. The properties of thin patterned magnetic films are therefore of importance.…”

“…In essence, the work presented here can be seen as an attempt to identify that shape of film (pattern) which should yield the narrowest FMR linewidth. Such experiments should have relevance in magnetic hybrid split ring resonator (SRR) metamolecules, where strong photon-magnon coupling occurs [2][3][4]. In the latter experiments, the permalloy and other magnetic films were simply patterned into small circular disks of ∼100 μm diameter, primarily to suppress eddy currents.…”

A Whole Surface of Exceptional Points

“…On the other hand, magnonic polaritons [31][32][33][34][35][36] have been emerging as a promising platform for non-Hermitian physics [37]. Strong coupling between magnons (quantization of collective spin excitations) and microwave photons has been demonstrated.…”