Imaging transition to fractional quantum Hall regime by Coulomb blockade microscopy

TL;DR

This paper investigates how Coulomb blockade microscopy can image the transition of electron systems in quantum dots to the fractional quantum Hall regime, revealing differences in charge density behavior at various magnetic fields.

Contribution

It introduces an exact diagonalization approach to analyze the reaction of electron systems to probe potentials, specifically focusing on the fractional quantum Hall transition in quantum dots.

Findings

Liquid-like response at integer Landau level fillings

Formation of charge density islands at fractional fillings

Imaging of molecular charge densities depends on symmetry

Abstract

We consider electron systems in quantum dots and imaging of the confined charge density by the Coulomb blockade microscopy (CBM) with the scanning probe technique. We apply an exact diagonalization method to study the reaction of the electron system to the potential induced by the model potential of the probe and calculate the energy maps as functions of the position of the probe. The charge densities derived from the energy maps are confronted to the exact charge densities. We focus on the transition of the electron system to the fractional quantum Hall conditions in external magnetic field. For magnetic fields corresponding to the integer fillings of the lowest Landau level the electron system exhibits a liquid-like reaction to the potential of the probe and the confined charge density can be quite accurately mapped by the CBM. For fractional fillings of the lowest Landau level the single-electron charge density islands nucleate in presence of the tip. In circular quantum dots the single-electron islands evade imaging by CBM. We demonstrate that mapping the molecular charge densities is possible for confinement potentials of symmetry that is lower and consistent with the geometry of the lowest-energy charge distribution of the single-electron islands.