Trions Stimulate Electronic Coupling in Colloidal Quantum Dot Molecules

TL;DR

This paper predicts that using trions instead of neutral excitons in colloidal quantum dot molecules enhances electron delocalization, potentially enabling room-temperature quantum entanglement with existing technology.

Contribution

It introduces a theoretical approach showing that trions restore electron delocalization in quantum dot molecules, overcoming previous limitations of weak coupling.

Findings

Trions improve electron delocalization in quantum dot dimers.

Positive trions are especially effective due to hole-hole repulsion.

Potential for room-temperature quantum entanglement with current tech.

Abstract

Recent synthetic progress has enabled the controlled fusion of colloidal CdSe/CdS quantum dots in order to form dimers manifesting electronic coupling in their optical response. While this ``artificial H2 molecule'' constitutes a milestone towards the development of nanocrystal chemistry, the strength of the coupling has proven to be smaller than intended. The reason is that, when an exciton is photo-induced in the system, the hole localizes inside the CdSe cores and captures the electron, thus preventing its delocalization all over the dimer. Here, we predict, by means of k$\cdot$p theory and configuration interaction calculations, that using trions instead of neutral excitons or biexcitons restores the electron delocalization. Positive trions are particularly apt because the strong hole-hole repulsion makes electron delocalization robust against moderate asymmetries in the cores, thus keeping a homodimer-like behavior. Trion-charged colloidal quantum dot molecules have the potential to display quantum entanglement features at room temperature with existing technology.