物理学报2026，Vol.75Issue(7)：25-32,8.DOI:10.7498/aps.75.20251473
La3Ni2O7常压下的关联电子特性
Correlated electronic properties of La3Ni2O7 at ambient pressure
摘要
Abstract
The newly discovered Ruddlesden-Popper(RP)-type bilayer lanthanum nickel oxide La3Ni2O7 has emerged as a pivotal candidate in high-temperature superconductivity research,following copper-based and iron-based superconductors.Its superconducting transition temperature reaching 80 K under high pressure has sparked intense interest,yet the correlated electronic properties under ambient pressure-an essential foundation for elucidating the superconducting mechanism—remain insufficiently understood.To address this gap,we systematically investigate the electronic structure and correlation effects of ambient-pressure La3Ni2O7 using a combined theoretical approach. First,we constructed an effective 11-orbital tight-binding model via density functional theory(DFT)calculations(implemented in VASP)with the projector augmented-wave(PAW)method,generalized gradient approximation(GGA-PBE)for exchange-correlation energy,and a cutoff energy of 600 eV.The model includes Ni's dz2 and dx2-y2 orbitals(dominant near the Fermi level)and seven O-p orbitals(including in-plane px/py,interlayer apical pz,and outer interlayer p′z/p″z orbitals),derived via Wannier90 orbital projection.Notably,the model reflects the charge-transfer nature of transition metal oxides,with indirect d-d hopping mediated by oxygen p orbitals instead of direct d-d transitions. We then employed cluster dynamical mean-field theory(CDMFT)to account for strong electronic correlations,a key limitation of conventional DFT in describing 3d transition metal oxides.The CDMFT calculations utilized the continuous-time quantum Monte Carlo(CTQMC)hybridization expansion(CTHYB)impurity solver(implemented in TRIQS-CTHYB)with β=25,Coulomb repulsion U=7 eV,Hund's coupling JH=0.7 eV,and double-counting corrections Ezdc=11.87 eV(for dz2)and Exdc=9.85 eV(for dx2-y2). Our results reveal three core physical findings: 1)Fermi liquid behavior and orbital-selective interlayer correlations:Ambient-pressure La3Ni2O7 exhibits a Fermi liquid phase,evidenced by the Matsubara self-energy Σ(iω)whose imaginary part vanishes near zero frequency.The orbital representation of Σ(iω)uncovers a non-zero interlayer self-energy for the dz2 orbital(mediated by oxygen p orbitals),while the interlayer self-energy of dx2-y2 is nearly zero—indicating pronounced interlayer correlations in dz2 orbitals that are absent in dx2-y2 orbitals(a result of higher-order Hund's coupling-mediated processes and lower electron density in dx2-y2). 2)Distinct electronic structure of dz2 bonding states:The local impurity Matsubara Green's function Gloc(iω)in the bonding-antibonding representation shows that the dz2 bonding state is uniquely occupied and located below the Fermi level(evidenced by a large positive real part at zero frequency),differing sharply from other bonding/antibonding states.The imaginary part of Gloc(iω)further indicates that the dx2-y2 antibonding state contributes the largest spectral weight near the Fermi level,followed by dz2 antibonding,dx2-y2 bonding,and dz2 bonding states. 3)Fermi surface topology and valley-like DOS near EF:Analytic continuation of the Matsubara self-energy to real frequencies reveals a valley-like structure in the orbital-resolved density of states(DOS)near the Fermi level,consistent with experimental observations of weak insulating behavior at ambient pressure.The upper peak of this valley(≈+0.07 eV)originates from quasiparticle dispersion near the Γ point(dominated by dz2 orbitals),while the lower peak(≈-0.07 eV)arises from flat bands along the Γ-X direction(dominated by dx2-y2 orbitals).The Fermi surface features α(electron-like,centered at Γ)and β(hole-like,centered at M)pockets,with the γ pocket absent-an observation that aligns well with angle-resolved photoemission spectroscopy(ARPES)measurements.Additionally,the real-frequency spectral function A(k,E)shows well-defined quasiparticle dispersion near EF and incoherent Hubbard bands at ω ≈±5 eV,while the interlayer apical oxygen pz orbitals contribute non-negligible weight near EF,confirming charge-transfer characteristics. Finally,we investigated the effect of Coulomb repulsion U(with fixed JH=0.7 eV)on interlayer correlations:increasing U enhances orbital renormalization(evidenced by the inverse renormalization factor Z-1=1-∂ImΣ(iω)/∂iω|iω→0)while reducing the magnitude of the dz2 interlayer self-energy(attributed to increased pd charge-transfer energy and reduced hopping probability). This study provides a comprehensive characterization of the correlated electronic properties of ambient-pressure La3Ni2O7,highlighting the critical role of dz2 interlayer correlations and Fermi surface topology in governing its ground state.These findings deepen our understanding of the material's ambient-pressure behavior.Future work will explore symmetry-breaking phases(e.g.,density waves,magnetism)using DMFT-based approaches,further advancing our understanding of nickel-based superconductors.关键词
La3Ni2O7/镍基超导体/关联效应/动力学平均场理论Key words
La3Ni2O7/nickel-based superconductors/correlation effect/dynamical mean-field theory引用本文复制引用
谢钟逸,罗志辉,姚道新..La3Ni2O7常压下的关联电子特性[J].物理学报,2026,75(7):25-32,8.基金项目
国家自然科学基金(批准号:12494591,92565303,92165204)、广东省磁电物性基础学科研究中心(物理学)(批准号:2024B0303390001)和广东省量子科学战略专项(批准号:GDZX2401010)资助的课题. Project supported by the National Natural Science Foundation of China(Grant Nos.12494591,92565303,92165204),the Research Center for Magnetoelectric Physics of Guangdong Province,China(Grant No.2024B0303390001),and the Guangdong Provincial Quantum Science Strategic Initiative,China(Grant No.GDZX2401010). （批准号:12494591,92565303,92165204）
