Direct observation of excitonic polaron in InAs/GaAs quantum dots

TL;DR

This paper reports the first direct observation of excitonic polarons in InAs/GaAs quantum dots through photoluminescence, revealing strong carrier-phonon interactions and challenging existing theoretical models.

Contribution

It provides the first direct experimental evidence of excitonic polarons in quantum dots and introduces a simple two-band model to explain the observations.

Findings

Observation of a new peak ($s'$) below the exciton ground state

Detection of a 31 meV anticrossing energy at 225 K

Evidence against Huang-Rhys formulism for carrier-phonon interaction

Abstract

Excitonic polaron is directly demonstrated for the first time in InAs/GaAs quantum dots with photoluminescence method. A new peak ($s'$) below the ground state of exciton ($s$) comes out as the temperature varies from 4.2 K to 285 K, and a huge anticrossing energy of 31 meV between $s'$ and $s$ is observed at 225 K, which can only be explained by the formation of excitonic polaron. The results also provide a strong evidence for the invalidity of Huang-Rhys formulism in dealing with carrier-longitudinal optical phonon interaction in quantum dot. Instead, we propose a simple two-band model, and it fits the experimental data quite well. The reason for the finding of the anticrossing is also discussed.