Screening by composite charged particles: the case of quantum well trions

TL;DR

This paper investigates how composite charged particles called trions influence the screening of external potentials in two-dimensional systems, revealing their dominant response and internal structure effects on dielectric properties.

Contribution

It provides a detailed analysis of trion screening effects within a random phase approximation, highlighting their behavior as point charges and their impact on dielectric response.

Findings

Trions dominate the dielectric response in mixtures with free electrons.

Trions behave as point charges with combined mass in the long wavelength limit.

Dielectric response is sensitive to the internal structure of trions at finite wave-vectors.

Abstract

We study the screening of an external potential produced by a two-dimensional gas of charged excitons (trions). We determine the contribution to the dielectric function induced by these composite charged particles within a random phase approximation. In mixtures of free electrons and trions, the trion response is found dominant. In the long wave-length limit, trions behave as point charges with mass equal to the sum of the three particle components. For finite wave-vectors, we show how the dielectric response is sensitive to the composite nature of trions and the internal degrees of freedom. Predictions are presented for the screening of a Coulomb potential, the scattering by charged impurities and the properties of trionic plasmons.