Towards identification of a non-abelian state: observation of a quarter of electron charge at $\nu=5/2$ quantum Hall state

TL;DR

This paper reports the observation of quasiparticles with charge e/4 in the $ u=5/2$ quantum Hall state, supporting the existence of non-abelian anyons which are promising for topological quantum computing.

Contribution

First experimental evidence of e/4 charge quasiparticles in the $ u=5/2$ state through shot noise measurements, advancing understanding of non-abelian quantum Hall states.

Findings

Quasiparticles with charge e/4 observed at $ u=5/2$

Charge e/2 and e inconsistent with data

Supports non-abelian anyon hypothesis

Abstract

The fractional quantum Hall effect, where plateaus in the Hall resistance at values of coexist with zeros in the longitudinal resistance, results from electron correlations in two dimensions under a strong magnetic field. Current flows along the edges carried by charged excitations (quasi particles) whose charge is a fraction of the electron charge. While earlier research concentrated on odd denominator fractional values of $\nu$, the observation of the even denominator $\nu=5/2$ state sparked a vast interest. This state is conjectured to be characterized by quasiparticles of charge e/4, whose statistics is non-abelian. In other words, interchanging of two quasi particles may modify the state of the system to an orthogonal one, and does not just add a phase as in for fermions or bosons. As such, these quasiparticles may be useful for the construction of a topological quantum computer. Here we report data of shot noise generated by partitioning edge currents in the $\nu=5/2$ state, consistent with the charge of the quasiparticle being e/4, and inconsistent with other potentially possible values, such as e/2 and e. While not proving the non-abelian nature of the $\nu=5/2$ state, this observation is the first step toward a full understanding of these new fractional charges.