Zero-energy edge states and chiral symmetry breaking at edges of graphite sheets

TL;DR

This paper explores zero-energy edge states in graphite sheets, their relation to chiral symmetry, and how electron interactions can induce magnetic or lattice distortions, with implications for carbon nanotubes.

Contribution

It reveals the connection between chiral symmetry and edge state-induced orders, and analyzes electron correlation effects in nanotubes using advanced theoretical methods.

Findings

Edge states form flat bands at Fermi energy.

Chiral symmetry underpins the existence of zero-energy edge states.

Electron interactions can lead to magnetic or lattice instabilities.

Abstract

Two-dimensional graphite sheets with a certain type of edges are known to support boundary states localized near the edges. Forming a flat band with a sharp peak in the density of states at the Fermi energy, they can trigger a magnetic instability or a distortion of the lattice in the presence of electron-electron or electron-phonon interactions. We shall discuss a relationship between chiral symmetry, which is the origin of the zero-energy edge states, and several types of induced orders such as spin density waves or lattice distortions. We also investigate electron correlation effects on the edge states for a wrapped quasi one-dimensional geometry, i.e., carbon nanotube, by means of the renormalization group and the open boundary bosonization.