Imaging backscattering through impurity-induced antidots in quantum Hall constrictions

TL;DR

This paper uses a scanning gate microscope to visualize and analyze backscattering in quantum Hall constrictions, revealing how localized states and disorder influence conductance fluctuations.

Contribution

It introduces a method to image backscattering processes and reconstruct the potential profile in quantum Hall devices, linking conductance fluctuations to localized states.

Findings

Backscattering events are mediated by localized states.

Conductance fluctuations are linked to potential disorder.

Imaging reveals conditions activating backscattering.

Abstract

We exploit the biased tip of a scanning gate microscope (SGM) to induce a controlled backscattering between counter-propagating edge channels in a wide constriction in the quantum Hall regime. We compare our detailed conductance maps with a numerical percolation model and demonstrate that conductance fluctuations observed in these devices as a function of the gate voltage originate from backscattering events mediated by localized states pinned by potential fluctuations. Our imaging technique allows us to identify the necessary conditions for the activation of these backscattering processes and also to reconstruct the constriction confinement potential profile and the underlying disorder.