Imaging of the Coulomb driven quantum Hall edge states

TL;DR

This paper uses a novel microwave impedance microscope to visualize and analyze the microscopic structure of quantum Hall edge states, revealing detailed electrostatic and magnetic field-dependent features.

Contribution

It introduces a new imaging technique for real-space mapping of quantum Hall edge and bulk states, providing detailed insights into their electrostatic and magnetic properties.

Findings

Edge strips' sizes and positions match electrostatic models

Microwave images reveal field-dependent evolution of edge states

Detailed microscopic information around the  quantum Hall state

Abstract

The edges of a two-dimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime are divided into alternating metallic and insulating strips, with their widths determined by the energy gaps of the QHE states and the electrostatic Coulomb interaction. Local probing of these submicrometer features, however, is challenging due to the buried 2DEG structures. Using a newly developed microwave impedance microscope, we demonstrate the real-space conductivity mapping of the edge and bulk states. The sizes, positions, and field dependence of the edge strips around the sample perimeter agree quantitatively with the self-consistent electrostatic picture. The evolution of microwave images as a function of magnetic fields provides rich microscopic information around the \nu = 2 QHE state.