Observation of e/4 charge at $\nu=1/2$ in GaAs

TL;DR

This study reports the first direct shot-noise measurements confirming e/4 charge quasiparticles at the ν=1/2 fractional quantum Hall state in GaAs, providing insights into its topological order and quasiparticle properties.

Contribution

First experimental evidence of e/4 charge quasiparticles at ν=1/2 in GaAs using shot-noise measurements with quantum point contacts.

Findings

Quasiparticles with charge e/4 observed at ν=1/2

Shot-noise measurements consistent across two devices

Provides a benchmark for topological order studies

Abstract

Even-denominator fractional quantum Hall states (FQHSs) fall outside the standard Laughlin's and Jain's odd-denominator hierarchy. In this work, we study the FQHS $\nu=1/2$ in the lowest Landau level. The state is confined within a 70 nm-wide GaAs quantum well, where the electrons exhibit a bilayer-like charge distribution. Inter-layer interactions stabilize the $\nu=1/2$ FQHS, which is predicted to host quasiparticles with charge e/4 - with either Abelian or non-Abelian topological order. Here, we report on shot-noise measurements of partitioned quasiparticles at $\nu=1/2$, where charge partitioning is generated by a unique etch-defined quantum point contact. Our measurements were performed on two nominally identical devices, at two independent experimental setups. Analysis of shot noise in the weak-backscattering regime in each device reveals quasiparticles with charge e/4. These observations provide a clear benchmark for future studies aimed at probing the topological order of the $\nu=1/2$ FQHS and its quasiparticles' exchange statistics.