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TT: Fachverband Tiefe Temperaturen
TT 23: Correlated Electrons – Poster I
TT 23.18: Poster
Montag, 9. März 2026, 18:00–20:00, P1
Ru L-edge RIXS on the dimer compound Ba3CeRu2O9: a cluster Mott insulator? — •Lara Pätzold1, Frederik Paech1, Enrico Bergamasco1, Henrik Schilling2, Anna Sandberg3, Hlynur Gretarsson4, Petra Becker-Bohatý2, Maria Hermanns3, and Markus Grüninger1 — 1II. Physikalisches Institut, University of Cologne, Germany — 2Kristallographie, University of Cologne, Germany — 3KOMKO, University of Stockholm, Sweden — 4DESY, Hamburg, Germany
Cluster Mott insulators host charge carriers in quasi-molecular orbitals on, e.g., dimers or tetramers [1-2]. With strong spin-orbit coupling, this may yield unconventional quasi-molecular magnetic moments tunable via, e.g., intracluster hopping. Cluster Mott insulators emerge in 5d transition-metal compounds due to large hopping, whereas in 3d materials one expects conventional Mott behavior with carriers localized on individual sites. To clarify whether cluster Mott insulators are realized in 4d compounds, we address the electronic structure of Ba3CeRu2O9 that hosts Ru2O9 dimers with 4 t2g holes. Ru L-edge RIXS and exact diagonalization reveal a rich excitation spectrum on top of an intricate non-magnetic ground state in the intermediate regime. Compared to 5d cluster Mott insulators, Ba3CeRu2O9 shows reduced intracluster hopping, smaller spin-orbit coupling, and larger electronic correlations, realizing an intriguing part of phase space.
[1] Revelli et al., Sci. Adv. 5, eaav4020 (2019).
[2] Magnaterra et al., PRL 133, 046501 (2024).
Keywords: cluster Mott insulators; ruthenates; strong spin-orbit coupling; correlated electrons; RIXS