Dynamical polarization, optical conductivity and plasmon mode of a linear triple component fermionic system

TL;DR

This paper studies the unique optical and electronic responses of linear triple component fermions, highlighting how their flat band alters plasmon modes, optical conductivity, and particle-hole excitations compared to Weyl fermions.

Contribution

It provides a detailed analysis of the dynamical polarization, dielectric function, and plasmon modes of a pseudospin-1 fermionic system, revealing significant differences from Weyl fermions due to the flat band.

Findings

Presence of a flat band modifies the particle-hole continuum.

Enhanced static polarization and reduced plasmon gap.

Shifted absorption edge and suppressed intercone transitions.

Abstract

We investigate the density and optical responses of a linear triple component fermionic system in both non-interacting and interacting regimes by computing its dynamical polarization function, RPA dielectric function, plasmon mode and long wavelength optical conductivity and compare the results with those of Weyl fermions and three-dimensional free electron gas. Linear triple component fermions are pseudospin-1 generalization of Weyl fermions, consisting of two linearly dispersive bands and a flat band. The presence of flat band brings about notable modifications in the response properties with respect to Weyl fermions such as induction of a new region in the particle-hole continuum, increased static polarization, reduced plasmon gap, shift in absorption edge, enhanced rate of increase in energy absorption with frequency and highly suppressed intercone transitions in the long wavelength limit. The plasmon dispersion follows the usual $\omega \sim \omega_0+ \omega_1 q^2$ nature as observed in other three-dimensional systems.