Regensburg 2025 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 17: Correlated Electrons: Method Development
TT 17.8: Talk
Tuesday, March 18, 2025, 11:30–11:45, H33
X-ray absorption meets Matrix Product States: Application of a MPS-based band Lanczos solver to impurity models with core levels — •Coraline Letouzé1, Sebastian Paeckel2, Guillaume Radtke1, and Benjamin Lenz1 — 1Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, 75005 Paris, France — 2Department of Physics, Arnold Sommerfeld Center for Theoretical Physics (ASC), Munich Center for Quantum Science and Technology (MCQST), Ludwig-Maximilians-Universität München, 80333 München, Germany
In strongly correlated materials like transition metal (TM) oxides, core-level spectroscopies such as X-ray Absorption Spectroscopy (XAS) are usually solved on a small cluster made of the valence and core states of the TM ion and its oxygen ligands. This cluster is then diagonalized exactly via the Lanczos algorithm. In the quest to extend this cluster model into an impurity model, beyond the capabilities of Exact Diagonalization, we apply the band Lanczos algorithm on Matrix Product States (MPS). Compared to standard valence-only impurity models, the inclusion of core levels leads to more interacting orbitals connected by an intricate interaction network.
In this talk I will present our results on impurity models for simple TM oxides (NiO, MnO), with a focus on the numerical stability and convergence of the MPS-based band Lanczos solver.
Keywords: impurity model; matrix product states; core-level spectroscopies; transition metal oxides; diagonalization