Non-Hermitian dispersion sign reversal of radiative resonances in two dimensions

TL;DR

This paper demonstrates that in two-dimensional systems, radiative resonances can exhibit a reversal of dispersion sign due to non-Hermitian effects, expanding understanding beyond cavity-based systems.

Contribution

It generalizes the phenomenon of mass-sign reversal in radiative resonances to two-dimensional materials without cavities and derives the conditions for this effect.

Findings

Mass-sign reversal occurs in 2D radiative resonances.

Conditions for sign reversal include a critical dephasing threshold.

The phenomenon persists in monolayer transition-metal dichalcogenides despite strong exchange interactions.

Abstract

In a recent publication [Wurdack et al., Nat. Comm. 14:1026 (2023)], it was shown that in microcavities containing atomically thin semiconductors non-Hermitian quantum mechanics can lead to negative exciton polariton masses. We show that mass-sign reversal can occur generally in radiative resonances in two dimensions (without cavity) and derive conditions for it (critical dephasing threshold etc.). In monolayer transition-metal dichalcogenides, this phenomenon is not invalidated by the strong electron-hole exchange interaction, which is known to make the exciton massless.