Resolving the orbital character of low-energy excitations in Mott insulator with intermediate spin-orbit coupling
Abstract Multi-band Mott insulators with moderate spin-orbit and Hund’s coupling are key reference points for theoretical concept developments of correlated electron systems. The ruthenate Mott insulator Ca 2 RuO 4 has therefore been intensively studied by spectroscopic probes. However, it has been challenging to resolve the fundamental excitations emerging from the hierarchy of electronic energy scales. Here we apply high resolution resonant inelastic x-ray scattering to probe deeper into the low-energy electronic excitations found in Ca 2 RuO 4 . In this fashion, we probe a series of spin-orbital excitations. By taking advantage of enhanced energy resolution, we probe a 40 meV mode through the oxygen K -edge. The polarization dependence of this low-energy excitations exposes a distinct orbital nature, originating from the interplay of spin-orbit coupling and octahedral rotations. Additionally, we discuss the role of magnetic correlations to describe the occurrence of excitations with amplitudes which are multiple of a given energy. Such direct determination of relevant electronic energy scales sharpens the target for theory developments of Mott insulators’ orbital degree of freedom.
Authors
- Stefano Agrestini (ORCID: https://orcid.org/0000-0002-3625-880X)
- Mario Cuoco (ORCID: https://orcid.org/0000-0002-7325-8331)
- Qisi Wang (ORCID: https://orcid.org/0000-0002-8741-7559)
- Ke‐Jin Zhou (ORCID: https://orcid.org/0000-0001-9293-0595)
- J. Chang (ORCID: https://orcid.org/0000-0002-4655-1516)
- Filomena Forte (ORCID: https://orcid.org/0000-0002-8112-1255)
- Mirian García‐Fernández (ORCID: https://orcid.org/0000-0002-6982-9066)
- A. Vecchione (ORCID: https://orcid.org/0000-0001-6848-6084)
- Jaewon Choi (ORCID: https://orcid.org/0000-0003-4616-4345)
- Karin von Arx (ORCID: https://orcid.org/0000-0002-8367-5454)
- Yasmine Sassa (ORCID: https://orcid.org/0000-0003-1416-5642)
- Leonardo Martinelli (ORCID: https://orcid.org/0000-0003-4978-8006)
- R. Fittipaldi (ORCID: https://orcid.org/0000-0003-2096-7983)
- Pascal Rothenbühler
Institutions
- University of Salerno (IT)
- Chinese University of Hong Kong (HK)
- University of Zurich (CH)
- Diamond Light Source (GB)
- Superconducting and other Innovative Materials and Devices Institute (IT)
- Chalmers University of Technology (SE)
- KTH Royal Institute of Technology (SE)
Publication Details
- Journal
- Communications Physics
- Published
- 2025-05-22
- DOI
- https://doi.org/10.1038/s42005-025-02104-2
- Primary Topic
- Magnetic and transport properties of perovskites and related materials
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- National Science Foundation
- Diamond Light Source
- European Commission
- Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
- Knut och Alice Wallenbergs Stiftelse
- Vetenskapsrådet
- Chinese University of Hong Kong
- Universität Zürich
- Ministero degli Affari Esteri e della Cooperazione Internazionale