First-principles many-body study of the electronic and optical properties of CsK2Sb, a semiconducting material for ultra-bright electron sources

TL;DR

This paper uses advanced first-principles calculations to thoroughly analyze the electronic and optical properties of CsK2Sb, aiming to improve understanding and modeling of its performance as a photocathode in ultra-bright electron sources.

Contribution

It provides detailed first-principles data on band structure and optical properties of CsK2Sb, incorporating many-body effects for the first time in this context.

Findings

Accurate band gap and dispersion data for CsK2Sb

Optical absorption characteristics relevant to photocathode performance

Insights into many-body effects on electronic properties

Abstract

We present a comprehensive first-principles investigation of the electronic and optical properties of CsK2Sb, a semiconducting material for ultra-bright electron sources for particle accelerators. Our study, based on density-fuctional theory and many-body perturbation theory, provides all the ingredients to model the emission of this material as a photocathode, including band gap, band dispersion, and optical absorption. An accurate description of these properties beyond the mean-field picture is relevant to take into account many-body effects. We discuss our results in the context of state-of-the-art electron sources for particle accelerators to set the stage towards improved modeling of quantum efficiency, intrinsic emittance, and other relevant quantities determining the macroscopic characteristics of photocathodes for ultra-bright beams.