Lindhard function, optical conductivity and plasmon mode of a linear triple component fermionic system

Bashab Dey, Tarun Kanti Ghosh

Published 2021-09-11Version 1

We investigate the nature of density response of linear triple component fermions by computing the Lindhard function, dielectric function, plasmon mode and long wavelength optical conductivity of the system and compare the results with those of Weyl fermions and three dimensional free electron gas. Linear triple component fermions are the low energy quasiparticles of linear triple component semimetals, consisting of linearly dispersive and dispersionless (flat band) excitations. 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, reduced plasmon energy gap, shift in absorption edge, enhanced rate of increase in energy absorption with frequency and forbidden 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 most of the three dimensional electronic systems.