Excitonic effects in the optical properties of CdSe nanowires

TL;DR

This paper investigates the optical properties of CdSe nanowires using advanced first-principle calculations, highlighting the importance of excitonic effects and local fields, and providing a model for optical gaps based on wire diameter.

Contribution

It introduces a first-principles approach that accounts for excitonic effects in nanowires, revealing limitations of bulk approximations and offering a predictive model for optical gaps.

Findings

Excitonic effects are crucial for accurate optical property predictions.

Bulk approximations fail at the nanoscale for CdSe nanowires.

A simple diameter-dependent model matches experimental data.

Abstract

Using a first-principle approach beyond density functional theory we calculate the electronic and optical properties of small diameter CdSe nanowires.Our results demonstrate how some approximations commonly used in bulk systems fail at this nano-scale level and how indispensable it is to include crystal local fields and excitonic effects to predict the unique optical properties of nanowires. From our results, we then construct a simple model that describes the optical gap as a function of the diameter of the wire, that turns out to be in excellent agreement with experiments for intermediate and large diameters.