Trion resonance in polariton-electron scattering

TL;DR

This paper develops a microscopic theory to analyze how trion resonances can enhance polariton-electron interactions in 2D semiconductor microcavities, revealing tunable and near-universal features relevant for optoelectronic applications.

Contribution

It introduces a universal low-energy scattering approximation for trion resonances in polariton-electron interactions, validated by full microscopic calculations.

Findings

Resonance position and magnitude depend on light-matter coupling and detuning.

The interaction strength is near universal, mainly influenced by coupling strength and trion binding energy.

The theory matches experimental observations in doped monolayer MoSe2.

Abstract

Strong interactions between charges and light-matter coupled quasiparticles offer an intriguing prospect with applications from optoelectronics to light-induced superconductivity. Here, we investigate how the interactions between electrons and exciton-polaritons in a two-dimensional semiconductor microcavity can be resonantly enhanced due to a strong coupling to a trion, i.e., an electron-exciton bound state. We develop a microscopic theory that uses a strongly screened interaction between charges to enable the summation of all possible diagrams in the polariton-electron scattering process. The position and magnitude of the resonance is found to vary depending on the values of the light-matter coupling and detuning, thus indicating a large degree of tunability. We furthermore derive an analytic approximation of the interaction strength based on universal lowenergy scattering theory. This is found to match extremely well with our full calculation, indicating that the trion resonance is near universal, depending more on the strength of the light-matter coupling relative to the trion binding energy rather than on the details of the electronic interactions. Thus, we expect the trion resonance in polariton-electron scattering to appear in a broad range of microcavity systems with few semiconductor layers, such as doped monolayer MoSe2 where such resonances have recently been observed experimentally [Sidler et al., Nature Physics 13, 255 (2017)].