Coexistence of sharp quasiparticle dispersions and disorder features in graphite

TL;DR

This study reveals that in disordered graphite, sharp quasiparticle dispersions can coexist with disorder features, explained by van Hove singularities, and demonstrates ARPES's potential for layered materials analysis despite crystal imperfections.

Contribution

It shows that ARPES can detect sharp dispersions in disordered graphite due to van Hove singularities, expanding the technique's applicability to imperfect layered materials.

Findings

Sharp quasiparticle dispersions along radial directions

Lack of dispersion along azimuthal directions

Observation of nondispersive features at band maxima and saddle points

Abstract

Angle resolved photoelectron spectroscopy (ARPES) on azimuthally disordered graphite demonstrates that sharp quasiparticle dispersions along the radial direction can coexist with a complete lack of dispersion along the azimuthal direction. This paradoxical coexistence can be explained in terms of van Hove singularities in the angular density of states. In addition, nondispersive features at the energies of band maxima and saddle points are observed and possible explanations are discussed. This work opens a possibility of studying the electronic structure of layered materials using ARPES even when large single crystals are difficult to obtain.