Pressure-Driven Evolution of Electronic and Magnetic Correlations in Bilayer Nickelate La₃Ni₂O₇

摘要

采用密度泛函理论、约束随机相近似与动力学平均场理论相结合的方法，系统研究了压力下双层镍酸盐La₃Ni₂O₇的电子和磁关联演化。计算表明，静水压增强层间跃迁和裸超交换能标，同时降低相对关联强度U/W，驱动体系整体趋向巡游态。尤为关键的是，轨道选择性演化清晰呈现：Ni dx²-y²态越发巡游，而Ni dz²轨道保持较强局域性，压力增强二者杂化，极大地放大了巡游电子对局域磁矩的近藤屏蔽效应。由此导致作为配对媒介的有效磁交换耦合在高压力区间被抑制，表明超导转变温度在高压下的单调下降源于近藤屏蔽压倒了超交换作用，为La₃Ni₂O₇的拱形超导相图提供了自洽的微观解释。

材料

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方法

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关键词

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亮点

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结论

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主要论断

• Hydrostatic pressure enhances interlayer hopping and the bare superexchange energy scale, while reducing the relative correlation strength U/W.
  • 证据: cRPA results show monotonic increase of t_perp and 4t2/U, and continuous decrease of U/W with pressure.
• The Ni dx2-y2 state becomes increasingly itinerant under pressure, whereas the Ni dz2 orbital retains a more localized character.
  • 证据: DMFT spectral functions show stronger renormalization of dz2 band.,Hybridization function of dx2-y2 is strongly enhanced near EF with pressure.
• Pressure‑enhanced hybridization amplifies the Kondo‑like screening of localized dz2 moments by itinerant dx2-y2 electrons.
  • 证据: DMFT local spin susceptibility decreases with pressure.,Extracted Kondo scale T_K increases by a factor ≈4 from 14.1 to 90 GPa.
• The effective interlayer magnetic exchange coupling J_eff is suppressed in the high‑pressure regime.
  • 证据: TB₂J calculations show peak in |J_⊥| near 45 GPa and subsequent reduction at higher pressures.,Orbital magnetic moments, especially dx2-y2, are quenched at high pressure.
• The monotonic decrease of T_c at high pressures is driven by the dominance of Kondo screening over superexchange interactions, explaining the dome‑shaped superconducting phase diagram.
  • 证据: Simultaneous increase of T_K and decrease of J_eff above the optimal pressure.,T_K reaches ≈400 K at 90 GPa, indicating efficient screening of moments needed for pairing.

研究流程

• DFT_and_Wannier_Construction — The low‑energy physics is reliably captured by a two‑orbital (dx2-y2, dz2) Wannier model.
  • 材料: La₃Ni₂O₇
  • 方法: DFT with WIEN₂k (FP-LAPW); PBE-GGA exchange-correlation; Wannier90 MLWF
  • 观察: Ni 3d orbitals dominate near EF; dz2 band nearly occupied and narrow; dx2-y2 band more dispersive; Excellent agreement between DFT and Wannier interpolation
• cRPA_Parameter_Derivation — Hydrostatic pressure enhances interlayer hopping and bare superexchange, but simultaneously reduces the relative correlation strength U/W.
  • 材料: La₃Ni₂O₇
  • 方法: Constrained Random Phase Approximation (cRPA) with projector method; Downfolding onto Ni 3d Wannier subspace
  • 观察: Screened U non‑monotonic, peaks around 30–60 GPa (≈2.9 eV) then decreases to ≈2.5 eV; Hund’s J nearly constant ≈0.65 eV; Bonding bandwidth W monotonically increases from ≈1.6 to 2.4 eV; U/W decreases continuously; Interlayer hopping t_perp and bare superexchange scale 4t2/U increase monotonically
• DFT+DMFT_Calculations — The dx2-y2 orbital becomes increasingly itinerant under pressure, dramatically amplifying the Kondo screening of the localized dz2 moments.
  • 材料: La₃Ni₂O₇
  • 方法: Charge‑self‑consistent DFT+DMFT (EDMFT code); CT‑HYB impurity solver; Maximum entropy analytic continuation
  • 观察: Orbital‑selective renormalization: dz2 band strongly renormalized, dx2-y2 more dispersive; dx2-y2 hybridization function strongly enhanced at EF with pressure; Local spin susceptibility χ_loc suppressed with pressure; Curie‑Weiss slope nearly constant → effective moment weakly pressure‑dependent; Weiss temperature intercept gives Kondo scale T_K that rises from ≈0.01 to ≈0.04 eV (≈ 116–464 K)
• Magnetic_Exchange_Calculations — The effective interlayer antiferromagnetic exchange is non‑monotonic and weakened at high pressure by itinerancy‑induced moment quenching.
  • 材料: La₃Ni₂O₇
  • 方法: Spin‑polarized DFT (ABACUS); TB₂J Green’s‑function method; Heisenberg model mapping
  • 观察: dz2 orbital carries the dominant magnetic moment, which decreases gradually; dx2-y2 moment strongly suppressed above 60 GPa; Nearest‑neighbour interlayer exchange J_⊥ is antiferromagnetic and non‑monotonic, peaking near 45 GPa (~ −7 meV) then suppressed; dx2-y2 channel contribution to J_⊥ much smaller than dz2 channel
• Synthesis_and_Interpretation — The dome‑shaped superconducting phase diagram arises from the competition between pressure‑enhanced superexchange and Kondo screening; at high pressure, excessive screening suppresses the pairing glue, causing the monotonic T_c decrease.
  • 方法: Comparison of cRPA, DMFT, and TB₂J trends; Estimation of Kondo scale T_K from local susceptibility
  • 观察: Bare superexchange 4t2/U increases monotonically, but effective exchange J_eff decreases at high pressure; Kondo screening scale T_K grows rapidly at high pressure; Local moments become increasingly screened above the optimal T_c region