Abstract

According to the orthodox paradigm, the partitioning of modes in a quantum point contact (QPC) geometry generates shot noise. The Fano factor thereof (assuming no further generated correlations) is the charge of the scattered quasi-particle. Applying this paradigm to edge modes of quantum Hall phases, if all modes are either transmitted or fully back-scattered (manifested as conductance plateaus), the shot noise should vanish. The surprising observation of recent experiments reveals nonzero noise even on conductance plateaus. Even more remarkable, in a number of different experimental setups, representing diverse quantum Hall phases and disparate geometries, the Fano factor of the plateau noise turns out to be equal to the bulk filling fraction (and not to the charge of the quasi-particles involved). To account for these observations we present a new theoretical paradigm of shot noise that relies on the ubiquitous presence of counterpropagating neutral edge modes (“neutralons”) at the edge. The origin of the neutral modes is different for various cases, either a topological (hole-like filling fractions) or edge reconstruction (particle-like or integer filling fractions). We show that even on an intermediate transmission plateau within the QPC shot noise can be generated via creating and then annihilating neutralons, leading to a Fano factor which is equal to the bulk filling fraction. We also show that this universal behavior survives off the conductance plateau.
∗ Sourav Biswas, Rajarshi Bhattacharyya, Hemanta Kumar Kundu, Moty Heiblum, Vladimir
Umansky, Moshe Goldstein, Yuval Gefen