Collective fermion excitation in a warm massless Dirac system

TL;DR

This paper predicts the existence of both normal and collective fermion modes, including plasmino, in warm 2D massless Dirac systems like graphene, highlighting key differences from QCD/QED systems.

Contribution

It introduces a self-consistent theoretical prediction of collective fermion excitations, including plasmino, in warm 2D Dirac systems, with novel thermal mass and dispersion properties.

Findings

Both fermion and plasmino modes are well-defined in warm Dirac systems.

The thermal mass scales as a_g^{3/4}T, differing from QED/QCD.

Distinct dispersion behaviors and degeneracies are observed between fermion and plasmino modes.

Abstract

Basing on a self-consistent method, we predict theoretically that there occurs not only a normal (quasi) fermion mode, but also a collective fermion mode, plasmino, in a warm 2D massless Dirac system, especially in a warm intrinsic graphene system. Results of Landau damping show that both fermion and plasmino are well defined modes. We find that there are sharp differences between the discussed system and the QCD/QED system. Firstly, the thermal mass is proportional to $\alpha_g^{3/4}T$ but not $\alpha_g T$. Secondly, at $0<q<q_c$, the fermion channel and plasmino channel are nearly degenerate and furthermore, the energy difference between fermion and plasmino becomes more and more larger with increasing $q$ at the region $q>q_c$. Thirdly, the fermion behaves as a "relativity particles" with none zero mass and the plasmino exhibits an anormal dispersion at moderate momentum.