Flat Bands near Fermi Level of Topological Line Defects on Graphite

TL;DR

This paper provides experimental evidence and theoretical analysis showing that one-dimensional topological defects on graphite host flat bands near the Fermi level, which are linked to dangling bonds of undercoordinated carbon atoms, potentially universal in graphene/graphite defects.

Contribution

It presents the first direct experimental observation of flat bands near the Fermi level in topological defects on graphite and explains their origin through ab initio calculations.

Findings

Flat bands are observed near the Fermi level in graphite defects.

Flat bands originate from dangling bonds of undercoordinated carbon atoms.

Flat bands may be a universal feature of 1D graphene/graphite defects.

Abstract

Flat bands play an important role in the study of strongly correlated phenomena, such as ferromagnetism, superconductivity, and fractional quantum Hall effect. Here we report direct experimental evidence for the presence of flat bands, close to the Fermi level, in one-dimensional topological defects on graphite seen as a pronounced peak in the tunnelling density of states. Our ab initio calculations indicate that the flat bands with vanishing Fermi velocity originate from sp2 dangling bonds (with antibonding nature) of undercoordinated carbon atoms at the edges of the defects. We further demonstrate that the presence of flat bands could be a universal behavior of 1D defects of graphene/graphite with undercoordinated carbon atoms at the edges of the defects.