Electron Correlations in an Electron Bilayer at Finite Temperature: Landau Damping of the Acoustic Plasmon

TL;DR

This study investigates the temperature-dependent Landau damping of acoustic plasmons in an electron bilayer, combining Raman scattering experiments with theoretical models, revealing limitations of static local field approximations at higher temperatures.

Contribution

The paper provides experimental data and compares it with theoretical models, highlighting the need for a dynamical local field approach to accurately describe exchange correlations at elevated temperatures.

Findings

Good agreement between experiment and theory for T_e < T_F/2

Static local field factors fail at T_e > T_F/2

Dynamical local field theory is necessary for accurate modeling

Abstract

We report angle-resolved Raman scattering observations of the temperature dependent Landau damping of the acoustic plasmon in an electron bilayer system realised in a GaAs double quantum well structure. Corresponding calculations of the charge-density excitation spectrum of the electron bilayer using forms of the random phase approximation (RPA), and the static local field formalism of Singwi, Tosi, Land and Sj\"{o}lander (STLS) extended to incorporate non-zero electron temperature $T_{\rm e}$ and phenomenological damping, are also presented. The STLS calculations include details of the temperature dependence of the intra- and inter-layer local field factors and pair-correlation functions. Good agreement between experiment and the various theories is obtained for the acoustic plasmon energy and damping for $T_{\rm e} \lesssim T_{\rm F}/2$, the Fermi temperature. However, contrary to current expectations, all of the calculations show significant departures from our experimental data for $T_{\rm e} \gtrsim T_{\rm F}/2$. From this, we go on to demonstrate unambiguously that real local field factors fail to provide a physically accurate description of exchange correlation behaviour in low dimensional electron gases. Our results suggest instead that one must resort to a {\em{dynamical}} local field theory, characterised by a {\em{complex}} field factor to provide a more accurate description.