The tunneling density-of-states of interacting massless Dirac fermions

TL;DR

This paper calculates the tunneling density-of-states in a clean 2D Dirac fermion system, revealing interaction-induced features such as a non-zero DOS at the Dirac point and plasmaron peaks, challenging disorder-based explanations.

Contribution

It provides a theoretical prediction that electron-electron interactions cause a finite DOS at the Dirac point, explaining experimental observations without disorder.

Findings

DOS grows linearly at high energies with suppressed slope due to velocity enhancement.

Plasmaron peaks appear at specific bias voltages depending on doping.

Finite DOS at the Dirac point is attributed to interactions, not disorder.

Abstract

We calculate the tunneling density-of-states (DOS) of a disorder-free two-dimensional interacting electron system with a massless-Dirac band Hamiltonian. The DOS exhibits two main features: i) linear growth at large energies with a slope that is suppressed by quasiparticle velocity enhancement, and ii) a rich structure of plasmaron peaks which appear at negative bias voltages in an n-doped sample and at positive bias voltages in a p-doped sample. We predict that the DOS at the Dirac point is non-zero even in the absence of disorder because of electron-electron interactions, and that it is then accurately proportional to the Fermi energy. The finite background DOS observed at the Dirac point of graphene sheets and topological insulator surfaces can therefore be an interaction effect rather than a disorder effect.