# Universal $1/3$-suppression of magnonic shot noise in diffusive insulating magnets

## TL;DR

This paper demonstrates a universal 1/3 suppression of magnonic shot noise in diffusive insulating magnets, similar to electron systems, despite the bosonic nature of magnons, and suggests experimental feasibility.

## Contribution

It extends Boltzmann-Langevin theory to magnons, revealing universal shot noise suppression in diffusive insulators regardless of quantum statistics.

## Key findings

- Magnonic shot noise is suppressed to 1/3 of Poissonian noise in diffusive insulators.
- The Fano factor at low temperatures shows universal behavior similar to electronic systems.
- Predictions are experimentally testable with current technology.

## Abstract

Extending a Boltzmann-Langevin theory to magnons, we show a universality of current-noise suppression in diffusive systems against the difference of quantum-statistical properties of bosons and fermions. To this end, starting from a quantum kinetic equation for magnons subjected to thermal gradient in dilute impurities, we derive a bosonic counterpart of the semiclassical Boltzmann-Langevin equation for electrons and evaluate a magnonic current-noise in the diffusive insulating magnet. We theoretically discover that compared with a Poissonian shot noise of magnons in an insulating ferromagnetic junction, the magnonic shot noise is suppressed in the diffusive insulating bulk magnet and noise-to-current ratio (Fano factor) at low temperatures exhibits a universal behavior, i.e., the same suppression $1/3$ as the one for electron transport in diffusive conductors, despite the difference of quantum-statistical properties. Finally, we show that our predictions are within experimental reach with current device and measurement technologies.