Is the charge determined via shot noise measurements unique?

TL;DR

This paper investigates how shot noise measurements of quasiparticle charge in fractional quantum Hall states depend on experimental conditions, revealing that measured charges can exceed theoretical predictions under certain weak backscattering and low-energy conditions.

Contribution

It demonstrates that tunneling quasiparticle charge measurements are not always unique and depend on measurement conditions, challenging the assumption of a fixed fundamental charge.

Findings

Measured quasiparticle charges vary with backscattering probability.

Higher-than-expected charges observed at low energies and weak backscattering.

Results suggest measurement conditions influence quasiparticle charge detection.

Abstract

Charged excitations in the fractional quantum Hall effect are known to carry fractional charges, as theoretically predicted and experimentally verified. Here we report on the dependence of the tunneling quasiparticle charge, as determined via highly sensitive shot noise measurements, on the measurement conditions, in the odd denominators states v=1/3 and v=7/3 and in the even denominator state v=5/2. In particular, for very weak backscattering probability and sufficiently small excitation energies (temperature and applied voltage), tunneling charges across a constriction were found to be significantly higher than the theoretically predicted fundamental quasiparticle charges.