Localized Distributions of Quasi Two-Dimensional Electronic States near Defects Artificially Created at Graphite Surfaces in Magnetic Fields

TL;DR

This study investigates how artificially created defects on graphite surfaces influence the local electronic states in high magnetic fields, revealing two distinct localized distributions and their energy-dependent transformation.

Contribution

It introduces new types of localized electronic distributions near defects in graphite, linked to defect potential depth, expanding understanding of quantum Hall states at surfaces.

Findings

Two localized distributions depend on defect potential depth

Gradual transition from localized to extended states with energy

Defect potential depth explains the distribution types

Abstract

We measured the local density of states of a quasi two-dimensional electron system (2DES) near defects, artificially created by Ar-ion sputtering, on surfaces of highly oriented pyrolytic graphite (HOPG) with scanning tunneling spectroscopy (STS) in high magnetic fields. At valley energies of the Landau level spectrum, we found two typical localized distributions of the 2DES depending on the defects. These are new types of distributions which are not observed in the previous STS work at the HOPG surface near a point defect [Y. Niimi \textit{et al}., Phys. Rev. Lett. {\bf 97}, 236804 (2006).]. With increasing energy, we observed gradual transformation from the localized distributions to the extended ones as expected for the integer quantum Hall state. We show that the defect potential depth is responsible for the two localized distributions from comparison with theoretical calculations.