来源 自动抓取
作者 Ziao Han, Lifen Xiang, Tianren Wang, Congcong Le, Jun Zhan, Siyi Lei, Sonia Francoual, Qisi Wang, Jiangping Hu, Tao Xiang, Ronny Sutarto, Xianxin Wu, X. J. Zhou, Zhihai Zhu
arXiv / 出版方 https://arxiv.org/abs/2610.01757
PDF https://arxiv.org/pdf/2610.01757
相关度评分 5.632
主分类 cond-mat.supr-con
发布日期 2026-10-02
研究范式 实验与理论
样品形态 薄膜

摘要

本文通过结合臭氧退火与等价稀土A位替代，在双层镍酸盐薄膜中有效施加c轴单轴压力并调控层间耦合，研究了自旋密度波（SDW）与类电荷各向异性序同超导的相互作用。共振弹性X射线散射显示，优化超导时SDW转变温度由150 K降至70 K，SDW虽被削弱但仍存在，而类电荷各向异性序在超导态被完全消除。极化分辨O K边X射线吸收谱与电子结构计算表明，A位替代引起的c轴压缩及臭氧退火填补层间氧空位，均增强层间Ni-O-Ni杂化，重构费米面并抑制SDW波矢附近的磁涨落，从而削弱SDW不稳定性。该结果说明两种电子序受不同能量尺度支配，并与自旋-无自旋条纹基态一致，为理解双层镍酸盐中密度波形成及其与超导的关系提供了新线索。

材料

方法

  • PLD
  • ozone-assisted annealing
  • resonant elastic X-ray scattering (REXS)
  • polarization-resolved O K-edge X-ray absorption spectroscopy (XAS)
  • X-ray linear dichroism (XLD)
  • hard X-ray diffraction
  • DFT
  • VASP
  • Wannier90
  • magnetic susceptibility calculations

关键词

亮点

  • Selectively suppresses two distinct electronic orders in bilayer nickelate thin films by tuning interlayer coupling through rare-earth A-site substitution and ozone annealing.
  • Realizes superconducting bilayer nickelate films with TSDW tuned from 150 K down to 70 K.
  • Shows that the charge-like anisotropy order is completely eliminated in the superconducting state while the SDW order persists but weakens.
  • Identifies two distinct routes—c-axis compression from A-site substitution and filling of interlayer oxygen vacancies by ozone annealing—that both enhance interlayer Ni-O-Ni hybridization.
  • Provides new constraints on the origin of density waves and their relationship to superconductivity in bilayer nickelates.

结论

  • Combining oxygen annealing with isovalent rare-earth A-site substitution effectively applies c-axis uniaxial pressure and realizes superconducting bilayer nickelate films with the SDW transition temperature suppressed from 150 K to 70 K.
  • While SDW order is weakened but remains, a second charge-like anisotropy order is completely eliminated in the superconducting state, showing that the two electronic orders are governed by different energy scales.
  • Polarization-resolved O K-edge X-ray absorption and electronic structure calculations show that strengthened interlayer coupling reconstructs the Fermi surface, reduces inter-pocket scattering, and weakens spin fluctuations near the SDW wavevector.
  • The findings are consistent with a spin–spinless stripe ground state; the suppression of SDW order can be explained by an itinerant Fermi-surface-driven scenario, whereas the disappearance of the charge-like anisotropy order points to the essential role of electronic correlations.

主要论断

  • Combining oxygen annealing with isovalent rare-earth A-site substitution effectively applies c-axis uniaxial pressure and tunes interlayer coupling, realizing superconducting bilayer nickelate films with TSDW suppressed from 150 K to 70 K.
    • 证据: Abstract: 'combine oxygen annealing with isovalent rare-earth (A-site) substitution to effectively apply c-axis uniaxial pressure, realizing superconducting bilayer nickelate films with TSDW suppressed from 150 K to 70 K.',Summary: combining ozone annealing and isovalent rare-earth A-site substitution tunes interlayer coupling and decreases SDW transition temperature from 150 K to 70 K upon optimizing superconductivity.
  • The SDW order is weakened but remains, while a second charge-like anisotropy order is completely eliminated in the superconducting state.
    • 证据: Abstract: 'while SDW order is weakened but remains, a second charge-like anisotropy order is completely eliminated in the superconducting state.',Full text: 'the SDW is progressively weakened but persists, whereas the channel charge-like order is completely eliminated upon substitution with Pr or Sm.',Full text: 'the charge-like anisotropy order is even more sensitive: its characteristic non-monotonic temperature profile … is completely suppressed once superconductivity is established.'
  • Polarization-resolved O K-edge X-ray absorption and electronic structure calculations show that strengthened interlayer coupling reconstructs the Fermi surface and weakens the SDW.
    • 证据: Abstract: 'Polarization-resolved O K-edge X-ray absorption and electronic structure calculations show that strengthened interlayer coupling reconstructs the Fermi surface and weakens the SDW.',Full text: 'This strain enhances the interlayer coupling, expanding the pocket while contracting the pocket. As a result, the inter-pocket scattering is reduced, which leads to a decrease in the odd-channel magnetic susceptibility near the SDW wavevector.'
  • The two electronic orders are governed by different energy scales and respond differently to the same tuning.
    • 证据: Full text: 'This selective suppression demonstrates that the two orders are not governed by a single energy scale.',Full text: 'the SDW weakens progressively as superconductivity is optimized, whereas the charge-like anisotropy order is completely eliminated.'
  • The results are consistent with a spin-spinless stripe ground state and suggest different roles for itinerant Fermi-surface nesting and electronic correlations.
    • 证据: Abstract: 'These findings, consistent with a spin-spinless stripe ground state, provide new insight into the mechanism of density wave formation and their interplay with superconductivity.',Full text conclusion: 'the suppression of the channel SDW order can be consistently explained by an itinerant, Fermi surface-driven scenario … the complete disappearance of the channel charge-like anisotropy order … points to the essential role of electronic correlations.'

研究流程

  • sample_preparation — Combining rare-earth A-site substitution and ozone annealing tunes interlayer coupling in bilayer nickelate thin films.
    • 材料: La2PrNi2O7-δ (LPNO) thin films; La3Ni2O7-δ (LNO) thin films; La2SmNi2O7-δ (LSNO) thin films; (001)-oriented LaAlO3 (LAO) substrates; (001)-oriented SrLaAlO4 (SLAO) substrates; stoichiometric polycrystalline target; ozone
    • 方法: pulsed laser deposition using a 248-nm KrF excimer laser; ozone-assisted annealing following an oxygen recycling protocol; X-ray reflectivity thickness calibration
    • 观察: Ozone annealing produced superconducting LPNO/SLAO films, whereas thicker LPNO/LAO films remained non-superconducting.; Ozone annealing fills interlayer oxygen vacancies and restores the Ni-O-Ni interlayer hybridization channel.
  • measurement — REXS and polarization-resolved XAS track the selective suppression of SDW and charge-like anisotropy orders and changes in interlayer hybridization.
    • 材料: LPNO/LAO films; LPNO/SLAO films; LNO/SLAO films; LSNO/SLAO films
    • 方法: resonant elastic X-ray scattering (REXS) at the Ni L-edge and O K-edge; polarization-resolved X-ray absorption spectroscopy (XAS) in total electron yield and total fluorescence yield modes; hard X-ray diffraction; temperature-dependent REXS momentum scans with Lorentzian peak fitting
    • 观察: REXS detects SDW order and a second charge-like anisotropy order with different polarization responses.; Ozone annealing suppresses the resonant peak intensity and shifts the SDW transition temperature.; The non-monotonic temperature profile of the charge-like anisotropy order disappears after ozone annealing.; O K-edge XAS out-of-plane spectra show restoration of low-energy spectral weight after ozone annealing, indicating increased interlayer hybridization.
  • analysis — Enhanced interlayer coupling reconstructs the Fermi surface and suppresses spin fluctuations near the SDW wavevector.
    • 材料: REXS data; XAS data; electronic structure models
    • 方法: band structure calculations using the projector augmented wave method in VASP; Perdew-Burke-Ernzerhof exchange-correlation functional; Wannier90 maximally localized Wannier functions for Ni orbitals; magnetic susceptibility evaluation; O K-edge XAS simulations using an excited-electron and core-hole approach; comparison of experimental spectra with calculated electronic structure
    • 观察: A-site substitution modeled as c-axis compression enhances interlayer coupling, expands the pocket, and contracts the pocket.; Enhanced interlayer coupling reduces inter-pocket scattering and decreases odd-channel magnetic susceptibility near the SDW wavevector.; Calculated O K-edge XAS links low-energy out-of-plane spectral weight primarily to interlayer apical oxygens.
  • interpretation — SDW suppression is consistent with an itinerant Fermi-surface-driven scenario, whereas elimination of the charge-like anisotropy order points to electronic correlations and the spin-spinless stripe framework.
    • 方法: unified framework combining REXS, XAS, hard X-ray diffraction, and first-principles calculations; comparison with the spin-spinless stripe framework
    • 观察: SDW order weakens but persists, while charge-like anisotropy order is completely eliminated in the superconducting state.; The temperature dependence of SDW integrated intensity shows no anomaly at Tc, indicating no direct competition between SDW order and superconductivity.; Selective suppression indicates that the two electronic orders are not governed by a single energy scale.