Dresden 2026 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 71: Ultrafast Phenomena

TT 71.6: Talk

Thursday, March 12, 2026, 10:45–11:00, HSZ/0103

Charged three-particle bound states at the L₂₃-edge in SrTiO₃ — •Sarah L. Görlitz¹, Widad Louafi², Sina Shokri¹, Martin Braß¹, Marc Merstorf¹, Jonas Hoecht¹, Kevin Ackermann¹, and Maurits W. Haverkort¹ — ¹Institut for Theoretical Physics, Heidelberg University, 69120 Heidelberg — ²Laboratory of Theoretical Physics, Faculty of Exact Sciences, University of Bejaia, 06000 Bejaia, Algeria

Few-body bound states underpin phenomena across physics-from hadronic three-body systems to excitons and trions in semiconductors-yet their formation and decay remain poorly understood.

We report analogous physics in bulk SrTiO₃ in Ti 2p → 3d core excitations. The XAS spectrum shows seven sharp peaks, understood from atomic physics as a Ti 2p hole interacting with a local Ti 3d electron in a cubic point group. Fluorescence and Auger-Meitner decay calculations explain the linewidth of the first four peaks but predict much sharper excitations than observed for the last two. Because these highest excited states are degenerate with the continuum, their broadening may arise if they are continuum excitations or resonances rather than bound excitons. To test this, we performed ab initio GW+BSE calculations, which agree with parameter-based atomic multiplet theory and reveal seven infinitely sharp excitons. In contrast, an Anderson-impurity model yields a finite linewidth for the highest excitons. We show that these are three-particle bound states composed of two locally bound Ti 3d electrons, one Ti 2p hole, and an additional free hole in the O 2p valence band.

Keywords: Electronic decay; Line-width; Core excited; Anderson Impurity