Breakdown of the static approximation for free carrier screening of excitons in monolayer semiconductors

TL;DR

This paper critically examines the static approximation used in modeling free carrier screening of excitons in monolayer semiconductors, revealing its limitations and proposing more accurate considerations based on many-body physics.

Contribution

It demonstrates that low-frequency static models significantly overestimate screening effects, emphasizing the need for dynamic approaches in exciton studies.

Findings

Static approximation overestimates free carrier response

Low-frequency models are inadequate for strongly bound excitons

High-level theories support the need for dynamic screening models

Abstract

We address the problem of free carrier screening of exciton states in two-dimensional monolayer semiconductors. Basic theoretical considerations are presented concerning the applicability of the commonly used static approximation of the screening effect and the implications are discussed. We show that the low-frequency models lead to a major overestimation of the free carrier response and are inadequate to describe the screening of strongly bound excitons in monolayer materials. The presented arguments are consistent with existing high-level many-body theories and transparently illustrate the underlying physics.