Regensburg 2025 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 92: Electronic Structure Theory

O 92.1: Vortrag

Donnerstag, 20. März 2025, 15:00–15:15, H25

Electronic and Optical properties of K-Sb and Na-Sb binary crystals from ab initio many-body theory — •Richard Schier and Caterina Cocchi — Carl von Ossietzky Universität Oldenburg, Institut für Physik

Alkali-based photocathode materials have come into the limelight as novel semiconducting materials for electron sources. However, challenges in sample purity and polycrystallinity hinder the direct experimental determination of their intrinsic properties. First-principles methods can effectively complement experiments in predicting favorable structures and gaining insight into their electronic and optical properties. In this work, we investigate K-Sb and Na-Sb binary crystals emerged as stable phases from high-throughput screening [1]. Using many-body perturbation theory on top of density functional theory, we find that all considered materials have optical gaps in the near-infrared region between 0.7 - 1.2 eV. The character of the excitations and electron-hole correlations therein are highly dependent on the composition and crystal structure of the compound. Excitonic effects appear more pronounced in the K-Sb crystals, where binding energies are of the order of 100 - 200 meV and the oscillator strength is sizably redistributed to lower-energy peaks. These characteristics indicate that K-Sb crystals are favorable candidates for efficient electron sources. [1] R. Schier, D. Guo, H.-D. Saßnick, and C. Cocchi, Adv. Theory Simulations (2024), https://doi.org/10.1002/adts.202400680.