Plasmon attenuation and optical conductivity of a two-dimensional electron gas

TL;DR

This paper investigates mechanisms of plasmon attenuation and optical conductivity in a ballistic two-dimensional electron gas, identifying processes beyond Landau damping that contribute to these phenomena.

Contribution

It identifies and evaluates new processes causing plasmon attenuation and optical conductivity in 2D electron gases, beyond Landau damping effects.

Findings

Landau damping does not cause plasmon attenuation in broad q range.

Processes like electron-hole pair excitation and plasmon-phonon conversion contribute to attenuation.

Quantitative estimates of linewidth and conductivity contributions are provided.

Abstract

In a ballistic two-dimensional electron gas, the Landau damping does not lead to plasmon attenuation in a broad interval of wave vectors q << k_F. Similarly, it does not contribute to the optical conductivity \sigma (\omega, q) in a wide domain of its arguments, E_F > \omega > qv_F, where E_F, k_F and v_F are, respectively, the Fermi energy, wavevector and velocity of the electrons. We identify processes that result in the plasmon attenuation in the absence of Landau damping. These processes are: the excitation of two electron-hole pairs, phonon-assisted excitation of one pair, and a direct plasmon-phonon conversion. We evaluate the corresponding contributions to the plasmon linewidth and to the optical conductivity.