Source capture
Authors Xiaoyang Chen, Wenliang Zhang, Fei Peng, Ting Cui, Guangdi Zhou, Zezhong Li, Jaewon Choi, Lizhi Xu, Yiu-Fung Chiu, Stefano Agrestini, Sahil Tippireddy, Haoliang Huang, Heng Wang, Xianfeng Wu, Peng Li, Jin-Feng Jia, Mirian Garcia-Fernandez, Yi Lu, Er-Jia Guo, Qi-Kun Xue, Zhuoyu Chen, Donglai Feng, Ke-Jin Zhou
arXiv / Publisher http://arxiv.org/abs/2604.21899v2
PDF https://arxiv.org/pdf/2604.21899v2
Relevance score 5.645
Primary category Not available in this batch.
Published Not available in this batch.
Research paradigm Experimental
Sample form Thin Film

Summary

This study utilized X-ray absorption spectroscopy and resonant inelastic X-ray scattering to independently control the strain and oxygen content of (La,Pr)3Ni2O7-δ thin films, tracking the microscopic evolution from a non-superconducting parent phase to a superconducting phase. The results demonstrate that both tuning methods induce delocalization of the oxygen 2p_z and nickel 3d_z2 orbitals, as evidenced by spectral weight transfer from the "upper Hubbard" peak to the hole peak in the O K-edge absorption spectra, accompanied by broadening and weakening of the Ni L-edge absorption spectra and dd excitations. Concurrently, the intensity and correlation length of the long-range spin density wave (SDW) order are significantly suppressed, indicating direct competition with superconductivity; while short-range magnons are damped, their bandwidth remains unchanged. This suggests that the delocalization of oxygen 2p_z and nickel 3d_z2 orbitals, along with the robustness of short-range magnons during the melting of the SDW order, are prerequisites for achieving superconductivity, thus providing constraints for theoretical models and pointing toward an orbital-selective pathway for designing nickel-based superconductors.

Materials

Methods

Keywords

Highlights

  • Two independent tuning knobs (strain and oxygen content) produce the same electronic evolution, establishing orbital delocalization as a key prerequisite.
  • The study provides spectroscopic constraints for theoretical models and an orbital-selective roadmap for designing nickelate superconductors.

Conclusions

  • Both compressive strain and oxygenation drive delocalization of O 2p_z and Ni 3d_z2 orbitals, evidenced by spectral weight transfer and broadening of excitations.
  • Long-range SDW order is suppressed in intensity and correlation length, showing direct competition with superconductivity.
  • Short-range magnons become damped but retain bandwidth, indicating robust short-range magnetic fluctuations.

Main claims

  • Both compressive strain and oxygenation drive delocalization of O 2p_z and Ni 3d_z2 orbitals, evidenced by spectral weight transfer from upper Hubbard peak to hole peak in O K-edge XAS and broadening of Ni L-edge XAS and dd excitations.
    • Evidence: The results demonstrate that both tuning methods induce delocalization of the oxygen 2p_z and nickel 3d_z2 orbitals, as evidenced by spectral weight transfer from the 'upper Hubbard' peak to the hole peak in the O K-edge absorption spectra, accompanied by broadening and weakening of the Ni L-edge absorption spectra and dd excitations.
  • Concurrently, the intensity and correlation length of the long-range spin density wave (SDW) order are significantly suppressed, indicating direct competition with superconductivity.
    • Evidence: Concurrently, the intensity and correlation length of the long-range spin density wave (SDW) order are significantly suppressed, indicating direct competition with superconductivity
  • Short-range magnons are damped but their bandwidth remains unchanged, suggesting that robust short-range magnons upon melting of SDW order are prerequisites for superconductivity.
    • Evidence: short-range magnons are damped, their bandwidth remains unchanged. This suggests that the delocalization of oxygen 2p_z and nickel 3d_z2 orbitals, along with the robustness of short-range magnons during the melting of the SDW order, are prerequisites for achieving superconductivity

Workflow

  • thin film growth — Two independent tuning routes (strain and oxygen content) effectively drive the system from insulating to superconducting state.
    • Materials: (La,Pr)3Ni2O7-δ thin films
    • Methods: pulsed laser deposition (PLD) for strain-tuning series; gigantic-oxidative atomic-layer-by-layer epitaxy (GAE) for oxygen content-tuning series
    • Observations: samples: non-SC LNO/LAO, non-SC LNO/SLAO1, non-SC LPNO/SLAO2, SC LPNO/SLAO3
  • X-ray absorption spectroscopy (XAS) measurement — Spectral weight transfer and broadening indicate delocalization of O 2p_z and Ni 3d_z2 orbitals.
    • Materials: (La,Pr)3Ni2O7-δ thin films
    • Methods: O K-edge XAS; Ni L-edge XAS
    • Observations: O K-edge: spectral weight transfer from 'Upper Hubbard' peak (B) to hole-like peak (A) in out-of-plane polarization; Ni L-edge: satellite feature broadens and weakens
  • Resonant inelastic X-ray scattering (RIXS) measurement — Short-range magnons persist with unchanged bandwidth, but long-range SDW order is suppressed.
    • Materials: (La,Pr)3Ni2O7-δ thin films
    • Methods: Ni L-edge RIXS
    • Observations: dd excitations become broadened and weakened; magnon damping increases; SDW order intensity and correlation length decrease
  • analysis of magnetic excitations and SDW — Long-range SDW order competes directly with superconductivity and is suppressed upon tuning, while short-range magnetic fluctuations remain robust.
    • Materials: (La,Pr)3Ni2O7-δ thin films
    • Methods: RIXS for magnon dispersion; resonant elastic X-ray scattering for SDW
    • Observations: SDW peak intensity and correlation length decrease with tuning, fully suppressed in SC sample; magnon damping increases but bandwidth unchanged