Spatially-resolved analysis of edge-channel equilibration in quantum Hall circuits

TL;DR

This paper presents a novel quantum Hall circuit with adjustable geometry using an AFM tip, revealing microscopic mechanisms of edge channel equilibration and demonstrating a beam mixer for quantum interferometry.

Contribution

It introduces a variable-geometry quantum Hall circuit with an AFM tip and experimentally demonstrates a beam mixer between co-propagating edge channels.

Findings

Edge channels equilibrate via microscopic mechanisms identified.

The circuit enables controlled charge transfer between channels.

Experimental results align with tight-binding simulations.

Abstract

We demonstrate an innovative quantum Hall circuit with variable geometry employing the moveable electrostatic potential induced by a biased atomic force microscope tip. We exploit this additional degree of freedom to identify the microscopic mechanisms that allow two co-propagating edge channels to equilibrate their charge imbalance. Experimental results are compared with tight-binding simulations based on a realistic model for the disorder potential. This work provides also an experimental realization of a beam mixer between co-propagating edge channels, a still elusive building block of a recently proposed new class of quantum interferometers.