Degenerate and non-degenerate parametric excitation in YIG nanostructures

TL;DR

This study explores how parametric excitation in YIG nanostructures can generate degenerate or non-degenerate magnon pairs, with potential applications in reciprocal-space computing due to controllable mode excitation.

Contribution

It provides experimental evidence and numerical analysis of magnon pair excitation modes in YIG disks, highlighting the ability to generate multiple modes simultaneously with fixed-frequency pumping.

Findings

Degenerate and non-degenerate magnon pairs can be excited depending on field orientation.

Frequency differences in magnon pairs range from 0.1 to 0.8 GHz.

Up to six modes can be excited simultaneously with monochromatic pumping.

Abstract

We study experimentally the processes of parametric excitation in microscopic magnetically saturated disks of nanometer-thick Yttrium Iron Garnet. We show that, depending on the relative orientation between the parametric pumping field and the static magnetization, excitation of either degenerate or non-degenerate magnon pairs is possible. In the latter case, which is particularly important for applications associated with the realization of computation in the reciprocal space, a single-frequency pumping can generate pairs of magnons whose frequencies correspond to different eigenmodes of the disk. We show that, depending on the size of the disk and the modes involved, the frequency difference in a pair can vary in the range 0.1-0.8 GHz. We demonstrate that in this system, one can easily realize a practically important situation where several magnon pairs share the same mode. We also observe the simultaneous generation of up to six different modes using a fixed-frequency monochromatic pumping. Our experimental findings are supported by numerical calculations that allow us to unambiguously identify the excited modes. Our results open new possibilities for the implementation of reciprocal-space computing making use of low damping magnetic insulators.