Shot noise as a diagnostic in the $\nu=2/3$ fractional quantum Hall edge zoo

TL;DR

This paper investigates shot noise in the fractional quantum Hall state at filling factor 2/3, revealing how different edge models produce distinct conductance plateaus and noise signatures, aiding experimental differentiation.

Contribution

It identifies mechanisms of shot noise generation across multiple conductance plateaus in the 2/3 fractional quantum Hall state, linking theoretical models to experimental observables.

Findings

Three conductance plateaus at e^2/2h, 5e^2/9h, and e^2/3h identified.

Distinct shot noise mechanisms proposed for each plateau.

Experimental signatures can distinguish between edge models.

Abstract

The $\nu = 2/3$ filling is the simplest paradigmatic example of a fractional quantum Hall state, which contains counter-propagating edge modes. These modes can be either in the unequilibrated regime or equilibrated to different extents, on top of a possible edge reconstruction. In the unequilibrated regime, two distinct renormalization group fixed points have been previously proposed, namely Kane-Fischer-Polchinski and Wang-Meir-Gefen. In the equilibration regime, different degree of thermal equilibration may occur, while charge is fully equilibrated. Here, we show that this rich variety of models can give rise to three possible conductance plateaus at $e^2/2h$ (recently observed in experiments), $5e^2/9h$ (predicted here), and $e^2/3h$ (observed earlier in experiments) in a quantum point contact geometry. We identify different mechanisms for \emph{electrical shot noise} generation at these plateaus, which provides an experimentally accessible venue for distinguishing among the distinct models.