Electronic structure of rare-earth infinite-layer RNiO2 (R = La, Nd)

The discovery of infinite-layer nickelate superconductor marks the new era in the field of superconductivity. In the rare-earth (R) nickelates RNiO2, although the Ni is also of d(9) electronic configuration, analogous to Cu d(9) in cuprates, whether electronic structures in infinite-layer nickelate are the same as cuprate and possess the single-band feature as well are still open questions. To illustrate the electronic structure of rare-earth infinite-layer nickelate, we perform first-principles calculations of LaNiO2 and NdNiO2 compounds and compare them with that of CaCuO2 using the hybrid functional method together with Wannier projection and group symmetry analysis. Our results indicate that the Ni d(x2- y2) in the LaNiO2 has weak hybridization with other orbitals and exhibits the characteristic single-band feature, whereas in NdNiO2, the Nd f orbital hybridizes with Ni d(x2- y2) and is a non-negligible ingredient for transport and even high-temperature superconductivity. Given that the Cu d(x2-y2) in cuprate strongly hybridizes with O 2p, the calculated band structures of nickelate imply some new band characters, which is worthy of more attention.