Bare LO-Phonon Peak in THz-Emission Signals: a Dielectric-Function Analysis

TL;DR

This paper analyzes coupled photocarrier-phonon dynamics in tellurium, revealing a persistent bare LO phonon mode at high carrier densities through dielectric function modeling, explaining recent THz-emission observations.

Contribution

It introduces a dielectric-function analysis showing the existence of a bare LO phonon mode at high carrier densities, which was not previously understood.

Findings

Existence of a bare LO phonon mode at high carrier density

The mode is an unscreened L-mode due to ineffective screening at large wave vectors

The analysis explains the bare LO-phonon peak observed in THz-emission spectra of Te

Abstract

We present a normal-mode analysis of coupled photocarrier-phonon dynamics in Te. We consider a dielectric function which accounts for LO phonons and the electron-hole gas within the Debye-Huckel model and RPA. Our main finding is the existence of a bare LO phonon mode in the system even at high carrier density. This oscillation is an unscreened L- mode arising from ineffective screening at large wave vectors. This mode is consistent with the bare LO-phonon peak in recent THz-emission spectra of Te.