Theory of unconventional superconductivity in nickelate-based materials

Based on the two-band tight-binding model composed of the 3d orbital of Ni and the 5d orbital of R (=La), we used the random-phase-approximation method to study the pairing symmetry of the nickelate superconductors. It is found that even without considering the coupling between the R and Ni orbitals, neither the antiferromagnetic spin-fluctuation pattern nor the doping-dependent behavior of the robust d_x²-y²-wave pairing state obtained in our calculations will be obviously influenced. Our results suggest the dominating role of the Ni 3d orbital in determining the low lying physics of the system. Furthermore, our results reveal a dome-shaped doping dependence of the superconducting transition temperature T_c, which is consistent with recent experiments.