# Explaining Observed Stability of Excitons in Highly Excited CdSe Nanoplatelets

## TL;DR

This paper provides a theoretical explanation for the observed stability of excitons in highly excited CdSe nanoplatelets, highlighting their unique behavior compared to bulk CdSe and suggesting the possibility of exciton superfluidity.

## Contribution

It offers a detailed theoretical analysis of exciton stability in CdSe nanoplatelets, explaining experimental results and predicting quantum degeneracy and superfluidity potential.

## Key findings

- Excitons in CdSe nanoplatelets remain stable at high densities.
- No crossover to electron-hole plasma occurs in studied density range.
- Quantum degenerate exciton gas likely observed, enabling superfluidity studies.

## Abstract

Two-dimensional electron-hole gases in colloidal semiconductors have a wide variety of applications. Therefore, a proper physical understanding of these materials is of great importance. In this paper we present a detailed theoretical analysis of the recent experimental results by Tomar et al., that show an unexpected stability of excitons in CdSe nanoplatelets at high photoexcitation densities. Including the screening effects by free charges on the exciton properties, our analysis shows that CdSe nanoplatelets behave very differently from bulk CdSe, and in particular do not show a crossover to an electron-hole plasma in the density range studied experimentally, even though there is substantial overlap between the excitons at the highest densities achieved. From our results we also conclude that a quantum degenerate exciton gas is realized in the experiments, which opens the prospect of observing superfluidity in CdSe nanoplatelets in the near future.