Study of the cavity-magnon-polariton transmission line shape

TL;DR

This paper combines experimental and theoretical approaches to analyze the microwave transmission line shape of cavity-magnon-polaritons, revealing asymmetric features and developing models that connect classical and microscopic descriptions.

Contribution

It introduces a comprehensive multi-level modeling framework for CMP transmission, linking classical oscillator, phase correlation, and Green's function approaches.

Findings

Fixed field measurements show Lorentzian line shapes.

Fixed frequency measurements reveal asymmetric line shapes.

The models accurately reproduce experimental spectra.

Abstract

We experimentally and theoretically investigate the microwave transmission line shape of the cavity-magnon-polariton (CMP) created by inserting a low damping magnetic insulator into a high quality 3D microwave cavity. While fixed field measurements are found to have the expected Lorentzian characteristic, at fixed frequencies the field swept line shape is in general asymmetric. Such fixed frequency measurements demonstrate that microwave transmission can be used to access magnetic characteristics of the CMP, such as the field line width $\Delta H$. By developing an effective oscillator model of the microwave transmission we show that these line shape features are general characteristics of harmonic coupling. At the same time, at the classical level the underlying physical mechanism of the CMP is electrodynamic phase correlation and a second model based on this principle also accurately reproduces the experimental line shape features. In order to understand the microscopic origin of the effective coupled oscillator model and to allow for future studies of CMP phenomena to extend into the quantum regime, we develop a third, microscopic description, based on a Green's function formalism. Using this method we calculate the transmission spectra and find good agreement with the experimental results.