Paramagnon softening upon doping in oxychloride cuprate superconductors
Abstract
Understanding how magnetic excitations and exchange interactions evolve with doping is crucial for deciphering the physics that shapes the phase diagram of high-temperature cuprate superconductors. Here, we clearly determine the behavior of the paramagnon dispersion in the oxychloride cuprate NaxCa2−xCuO2Cl2 up to the highest doping level. We find that the paramagnon bandwidth, defined by the energy at the X zone boundary $(0.5,0,0)$, remains unchanged within experimental uncertainty, even though it exhibits significant broadening. In contrast, along the nodal direction Γ−M (\textit{i.e.}, from (0,0,0) to $(0.5,0.5,0)$), the paramagnon energy shows a marked softening with doping, with a shift of up to ΔE∼150 meV at the midpoint of the zone for the highest doping, which is about half of its initial value in the antiferromagnetic phase. Calculations of the dynamical spin structure factor for a one-band Hubbard model, including hopping terms up to the third-nearest neighbor (t′′), explain this behavior and accurately reproduce the observed wave vector dependence and directional variation in the Brillouin zone.
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BibTeX
@misc{fawaz2026paramagnon,
title = {{Paramagnon softening upon doping in oxychloride cuprate superconductors}},
author = {Chafic Fawaz and Léo Gaspard and Laura Chaix and Luca Laveder and Benjamin Bacq-Labreuil and Victor Porée and Flora Yakhou-Harris and Kurt Kummer and Nicholas B. Brookes and Alessandro Nicolaou and Hajime Yamamoto and Yuichi Okazaki and Ikuya Yamada and Masaki Azuma and David Santos-Cottin and Marie-Aude Méasson and Benjamin Lenz and Matteo d'Astuto},
howpublished = {HAL},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.05160},
eprint = {2610.05160},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05789846v1},
note = {CC BY-ND 4.0},
}
RIS
TY - UNPB
TI - Paramagnon softening upon doping in oxychloride cuprate superconductors
AU - Chafic Fawaz
AU - Léo Gaspard
AU - Laura Chaix
AU - Luca Laveder
AU - Benjamin Bacq-Labreuil
AU - Victor Porée
AU - Flora Yakhou-Harris
AU - Kurt Kummer
AU - Nicholas B. Brookes
AU - Alessandro Nicolaou
AU - Hajime Yamamoto
AU - Yuichi Okazaki
AU - Ikuya Yamada
AU - Masaki Azuma
AU - David Santos-Cottin
AU - Marie-Aude Méasson
AU - Benjamin Lenz
AU - Matteo d'Astuto
PY - 2026
DA - 2026/10/07
PB - HAL
DO - 10.48550/arxiv.2610.05160
UR - https://hal.science/hal-05789846v1
AB - Understanding how magnetic excitations and exchange interactions evolve with doping is crucial for deciphering the physics that shapes the phase diagram of high-temperature cuprate superconductors. Here, we clearly determine the behavior of the paramagnon dispersion in the oxychloride cuprate Na_xCa_2−xCuO_2Cl_2 up to the highest doping level. We find that the paramagnon bandwidth, defined by the energy at the X zone boundary $(0.5,0,0)$, remains unchanged within experimental uncertainty, even though it exhibits significant broadening. In contrast, along the nodal direction Γ−M (\textit{i.e.}, from (0,0,0) to $(0.5,0.5,0)$), the paramagnon energy shows a marked softening with doping, with a shift of up to ΔE∼150 meV at the midpoint of the zone for the highest doping, which is about half of its initial value in the antiferromagnetic phase. Calculations of the dynamical spin structure factor for a one-band Hubbard model, including hopping terms up to the third-nearest neighbor (t^′′), explain this behavior and accurately reproduce the observed wave vector dependence and directional variation in the Brillouin zone.
ER -