Polarized Superradiance from CsPbBr3 Quantum Dot Superlattice with Controlled Inter-dot Electronic Coupling

TL;DR

This paper reports the first observation of polarized superradiance with narrow linewidth and large redshift from electronically coupled CsPbBr3 quantum dot superlattices, highlighting the role of anisotropic electronic coupling.

Contribution

It demonstrates polarized superradiance in perovskite QD superlattices achieved through ligand engineering and strong quantum confinement, a novel observation in this material system.

Findings

Polarized superradiance with <5 meV linewidth observed.

Large redshift (~200 meV) indicates strong electronic coupling.

Superradiance exhibits photon bunching at low excitation densities.

Abstract

Cooperative emission of photons from an ensemble of quantum dots (QDs) as superradiance can arise from the electronically coupled QDs with a coherent emitting excited state. This contrasts with superfluorescence (Dicke superradiance), where the cooperative photon emission occurs via a spontaneous buildup of coherence in an ensemble of incoherently excited QDs via their coupling to a common radiation mode. While superfluorescence has been observed in perovskite QD systems, reports of superradiance from the electronically coupled ensemble of perovskite QDs are rare. Here, we demonstrate the generation of polarized superradiance with a very narrow linewidth (<5 meV) and a large redshift (~200 meV) from the electronically coupled CsPbBr3 QD superlattice achieved through a combination of strong quantum confinement and ligand engineering. In addition to photon bunching at low excitation densities, the superradiance is polarized in contrast to the uncoupled exciton emission from the same superlattice. This finding suggests the potential for obtaining polarized cooperative photon emission via anisotropic electronic coupling in QD superlattices even when the intrinsic anisotropy of exciton transition in individual QDs is weak.