Recent photoemission experiments on the quasi-one-dimensional Ba-based cuprates suggest that doped holes experience an attractive potential not captured using the simple Hubbard model. This observation has garnered significant attention due to its potential relevance to Cooper pair formation in high-Tc cuprate superconductors. To scrutinize this assertion, we examined signatures of such an attractive potential in doped 1D cuprates Ba2CuO3+δ by measuring the dispersion of the 2-spinon excitations using Cu L3-edge resonant inelastic X-ray scattering (RIXS). Upon doping, the 2-spinon excitations appear to weaken, with a shift of the minimal position corresponding to the nesting vector of the Fermi points, qF. Notably, we find that the energy scale of the 2-spinons near the Brillouin zone boundary is substantially softened compared to that predicted by the Hubbard model in one-dimension. Such a discrepancy implies missing ingredients, which lends support for the presence of an additional attractive potential between holes.
@article{arxiv.2502.21316,
title = {Doping dependence of 2-spinon excitations in the doped 1D cuprate Ba$_2$CuO$_{3+{\delta}}$},
author = {Jiarui Li and Daniel Jost and Ta Tang and Ruohan Wang and Yong Zhong and Zhuoyu Chen and Mirian Garcia-Fernandez and Jonathan Pelliciari and Valentina Bisogni and Brian Moritz and Kejin Zhou and Yao Wang and Thomas P. Devereaux and Wei-Sheng Lee and Zhi-Xun Shen},
journal= {arXiv preprint arXiv:2502.21316},
year = {2025}
}