Effective Bi-Layer Model Hamiltonian and Density-Matrix Renormalization Group Study for the High-TcSuperconductivity in La_(3)Ni_(2)O_(7) under High Pressure  

作　　者：沈阳 秦明普 张广铭 Yang Shen;Mingpu Qin;Guang-Ming Zhang(Key Laboratory of Artificial Structures and Quantum Control,School of Physics and Astronomy,Shanghai Jiao Tong University,Shanghai 200240,China;Hefei National Laboratory,Hefei 230088,China;State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics,Tsinghua University,Beijing 100084,China;Frontier Science Center for Quantum Information,Beijing 100084,China)

机构地区：[1]Key Laboratory of Artificial Structures and Quantum Control,School of Physics and Astronomy,Shanghai Jiao Tong University,Shanghai 200240,China [2]Hefei National Laboratory,Hefei 230088,China [3]State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics,Tsinghua University,Beijing 100084,China [4]Frontier Science Center for Quantum Information,Beijing 100084,China

出　　处：《Chinese Physics Letters》2023年第12期138-142,共5页中国物理快报（英文版）

基　　金：the support from the National Key Research and Development Program of China(Grant No.2017YFA0302902);the support from the National Key Research and Development Program of China(Grant No.2022YFA1405400);the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0301902);the National Natural Science Foundation of China(Grant No.12274290);the Sponsorship from Yangyang Development Fund。

摘　　要：High-T_(c)superconductivity with possible T_(c)≈80 K has been reported in the single crystal of La_(3)Ni_(2)O_(7)under high pressure.Based on the electronic structure given by the density functional theory calculations,we propose an effective bi-layer model Hamiltonian including both 3d_(z)^(2)and 3d_((x)^(2)-(y)^(2))orbital electrons of the nickel cations.The main feature of the model is that the 3d_(z)^(2)electrons form inter-layerσ-bonding and anti-bonding bands via the apical oxygen anions between the two layers,while the 3d_((x)^(2)-(y)^(2))electrons hybridize with the 3d_(z)^(2)electrons within each NiO_(2)plane.The chemical potential difference of these two orbital electrons ensures that the 3d_(z)^(2)orbitals are close to half-filling and the 3d_((x)^(2)-(y)^(2))orbitals are near quarter-filling.The strong on-site Hubbard repulsion of the 3d_(z)^(2)orbital electrons gives rise to an effective inter-layer antiferromagnetic spin super-exchange J.Applying pressure can self dope holes on the 3d_(z)^(2)orbitals with the same amount of electrons doped on the 3d_((x)^(2)-(y)^(2))orbitals.By performing numerical density-matrix renormalization group calculations on a minimum setup and focusing on the limit of large J and small doping of 3d_(z)^(2)orbitals,we find the superconducting instability on both the 3d_(z)^(2)and3d_((x)^(2)-(y)^(2))orbitals by calculating the equal-time spin singlet pair–pair correlation function.Our numerical results may provide useful insights in the high-T_(c)superconductivity in single crystal La_(3)Ni_(2)O_(7)under high pressure.

关 键 词：function HAMILTONIAN ORBITAL 

分 类 号：O469[理学—凝聚态物理]