Abstract
Recently,a bulk nickelate superconductor La3Ni2O7 is discovered at pressures with a remarkable high transition temperature Tc～80 K.Here,we study a Hubbard model with tight-binding parameters derived from ab initio calculations of La3Ni2O7,by employing large scale determinant quantum Monte Carlo and cellular dynamical mean-field theory.Our result suggests that the superexchange couplings in this system are comparable to that of cuprates.The system is a charge transfer insulator as the hole concentration becomes four per site at large Hubbard U.Upon hole doping,two low-energy spin-singlet bands emerge in the system exhibiting distinct correlation properties:while the one composed of the out-of-plane Ni-d3z2-r2 and O-pz orbitals demonstrates strong antiferromagnetic correlations and narrow effective bandwidth,the in-plane singlet band consisting of the Ni-dx2-y2 and O-px/py orbitals is in general more itinerant.Over a broad range of hole doping,the doped holes occupy primarily the dx2-y2 and px/py orbitals,whereas the d3z2-r2 and pz orbitals retain underdoped.We propose an effective t-J model to capture the relevant physics and discuss the implications of our result for comprehending the La3Ni2O7 superconductivity.
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