# Microwave photons emitted by fractionally charged quasiparticles

## TL;DR

This paper demonstrates a universal microwave photon measurement method to unambiguously determine fractional charge and exclusion statistics of quasiparticles in strongly correlated systems, advancing the exploration of anyonic statistics.

## Contribution

It introduces a novel microwave photon emission technique to identify fractional charge and statistics of quasiparticles, validated by universal fluctuation relations.

## Key findings

- Photons emitted only at frequencies below qV_dc/h reveal fractional charge.
- The threshold frequency directly measures quasiparticle charge q.
- Results agree with predictions from the Luttinger model and fluctuation relations.

## Abstract

Strongly correlated low-dimensional systems can host exotic elementary excitations carrying a fractional charge $q$ and potentially obeying anyonic statistics. In the fractional quantum Hall effect, their fractional charge has been successfully determined owing to low frequency shot noise measurements. However, a universal method for sensing them unambiguously and unraveling their intricate dynamics was still lacking. Here, we demonstrate that this can be achieved by measuring the microwave photons emitted by such excitations when they are transferred through a potential barrier biased with a dc voltage $V_{\text{dc}}$. We observe that only photons at frequencies $f$ below $qV_{\text{dc}}/h$ are emitted. This threshold provides a direct and unambiguous determination of the charge $q$, and a signature of exclusion statistics. Derived initially within the Luttinger model, this feature is also predicted by universal non-equilibrium fluctuation relations which agree fully with our measurements. Our work paves the way for further exploration of anyonic statistics using microwave measurements.