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Evolution of spin excitations in superconducting La2−xCaxCuO4−δ from the underdoped to the heavily overdoped regime

S. Hameed1,*, Y. Liu1, M. Knauft1, K. S. Rabinovich1, G. Kim1, G. Christiani1, G. Logvenov1, F. Yakhou-Harris2, A. V. Boris1 et al.

B. Keimer1,† and M. Minola1,‡

  • *Contact author: s.hameed@fkf.mpg.de
  • †Contact author: b.keimer@fkf.mpg.de
  • ‡Contact author: m.minola@fkf.mpg.de
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Phys. Rev. B 114, 074513 – Published 27 August, 2026

DOI: https://doi.org/10.1103/kvpz-x64t

Abstract

We investigate high-energy spin excitations in hole-doped La2−xCaxCuO4−δ (LCCO) films across a broad Ca doping range (x=0.05–0.50) using resonant inelastic x-ray scattering (RIXS). Polarization analysis and incident-photon energy detuning measurements confirm the persistence of collective paramagnon excitations up to x=0.50. Consistent with previous studies on other cuprate families, we observe a pronounced crossover near x=0.15, where paramagnon spectral weight is transferred to incoherent spin-flip excitations associated with the particle-hole continuum. The overall behavior of paramagnons in LCCO resembles that in other hole-doped cuprates and appears insensitive to the persistence of superconductivity at high doping levels in LCCO—up to at least x=0.50, as demonstrated in prior work. These findings support the view that high-energy magnetic excitations probed by RIXS are not a major contributor to superconducting pairing, in line with theories of spin-fluctuation mediated superconductivity.

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Phys. Rev. B 114, 074513– Published 27 August, 2026
  • Received 3 September 2025
  • Accepted 13 August 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by Max Planck Society.

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