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

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.

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• Exploring the Cs-Te phase space via high-throughput density-functional theory calculations beyond the generalized-gradient approximation
• Stability and electronic properties of CsK${}_2$Sb surface facets
• Thermoelectric transport of strained CsK${}_2$Sb: The role of electron velocities and scattering within extended Fermi surfaces