Magnetic Excitations of a Half-Filled Tl-based Cuprate
Journal article, 2026
Strong electron correlations drive Mott insulator transitions. Yet, there exists no framework to classify Mott insulators by their degree of correlation. Cuprate superconductors, with their tunable doping and rich phase diagrams, offer a unique platform to investigate the evolution of these interactions. However, spectroscopic access to a clean half-filled Mott-insulating state is lacking in compounds with the highest superconducting onset temperature. To fill this gap, we introduce a pristine, half-filled thallium-based cuprate system, Tl2Ba5Cu4Ox. Using high-resolution resonant inelastic x-ray scattering, we probe long-lived magnon excitations and uncover a pronounced kink in the magnon dispersion, marked by a simultaneous change in group velocity and lifetime broadening. Modeling the dispersion within a Hubbard-Heisenberg approach, we extract the interaction strength and compare it with other cuprate systems. Our results establish a cuprate universal relation between electron-electron interaction and magnon zone-boundary dispersion. Superconductivity seems to be optimal at intermediate correlation strength, suggesting an optimal balance between localization and itinerancy.
Author
I. Biało
University of Zürich
Q. Wang
Chinese University of Hong Kong
Julia Küspert
University of Zürich
European Synchrotron Radiation Facility (ESRF)
X. Hong
University of Zürich
Chinese University of Hong Kong
L. Martinelli
University of Zürich
O. Gerguri
Paul Scherrer Institut
University of Zürich
Y. Chan
Chinese University of Hong Kong
K. Von Arx
University of Zürich
Ola Kenji Forslund
Uppsala University
University of Zürich
W. R. Pudelko
Paul Scherrer Institut
University of Zürich
C. Lin
Stanford Synchrotron Radiation Laboratory
University of Zürich
N. C. Plumb
Paul Scherrer Institut
Yasmine Sassa
Chalmers, Physics, Materials Physics
Royal Institute of Technology (KTH)
Davide Betto
European Synchrotron Radiation Facility (ESRF)
Nicholas B. Brookes
European Synchrotron Radiation Facility (ESRF)
M. Rosmus
University Paris-Saclay
Jagiellonian University in Kraków
N. Olszowska
Jagiellonian University in Kraków
Matthew D. Watson
Diamond Light Source
T. K. Kim
Diamond Light Source
C. Cacho
Diamond Light Source
M. Horio
University of Tokyo
M. Ishikado
Comprehensive Research Organization for Science and Society (CROSS)
H. M. Rønnow
Swiss Federal Institute of Technology in Lausanne (EPFL)
J. Chang
University of Zürich
Communications Materials
26624443 (eISSN)
Vol. 7 1 50Subject Categories (SSIF 2025)
Atom and Molecular Physics and Optics
Condensed Matter Physics
DOI
10.1038/s43246-025-01061-1