Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

HL: Fachverband Halbleiterphysik

HL 11: Ultra-fast Phenomena I

HL 11.6: Vortrag

Montag, 17. März 2025, 17:30–17:45, H14

Ultrafast Dynamic Coulomb Screening of X-ray Core Excitons in Photoexcited Semiconductors — •Thomas C. Rossi¹, Lu Qiao², Conner P. Dykstra³, Ronaldo Rodrigues Pela⁴, Richard Gnewkow^1,5, Rachel Wallick³, John H. Burke³, Erin Nicholas³, Anne-Marie March⁶, Gilles Doumy⁶, D. Bruce Buchholz⁷, Christiane Deparis⁸, Jesus Zuñiga-Pérez^8,9, Michael Weise¹⁰, Klaus Ellmer¹⁰, Mattis Fondell¹, Claudia Draxl², and Renske M. van der Veen^1,5,11 — ¹Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany — ²Department of Physics and CSMB, Humboldt Universität zu Berlin, Berlin, Germany — ³Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA — ⁴Supercomputing Department, Zuse Institute Berlin (ZIB), Berlin, Germany — ⁵Institute of Optics and Atomic Physics, Technische Universität Berlin, Berlin, Germany — ⁶Chemical Sciences and Engineering Division, Argonne National Laboratories, Lemont, Illinois, USA — ⁷Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States — ⁸Université Côte d’Azur, CNRS, CRHEA, rue Bernard Gregory, Sophia Antipolis, Valbonne, France — ⁹Majulab, International Research Centre Laboratory IRL 3654, Singapore — ¹⁰Optotransmitter-Umweltschutz-Technologie (OUT) e.V., Berlin, Germany — ¹¹Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA

The screening of core excitons is an inherent many-body process that can reveal insight into charge-transfer excitations and electronic correlations. Here we demonstrate the dynamic Coulomb screening induced by photoexcited carriers on core excitons employing X-ray transient absorption (XTA) spectroscopy with picosecond time resolution. Our interpretation is supported by state-of-the-art ab initio calculations including many-body perturbation theory. Using ZnO as an archetypal wide band-gap semiconductor, we show that the Coulomb screening modification at the Zn L₃- and K-edge leads to a decrease in the core-exciton binding energy. We also theoretically predict the effect of core-exciton screening on the femtosecond time scale for the case of ZnO, a major step towards hard X-ray excitonics. The results have implications for the interpretation of ultrafast X-ray spectra in general and their use in tracking charge carrier dynamics in complex materials on atomic length scales.

Keywords: X-ray Absorption Spectroscopy; Zinc Oxide; Core Exciton; Coulomb Screening; Bethe-Salpeter Equation