Nickelate superconductivity —A systematic computational design of dynamically stable <i>d⁹</i> nickelates

The origin of superconductivity in the Sr-doped layered nickelate NdNiO₂ has been studied actively since its recent discovery [1]. Several theoretical studies, including our own [2], have shown that the electronic structure of NdNiO₂ is quite similar to that of the cuprates near the Fermi level, but they are different in that the Ni 3d_x²-y² orbital is self-doped due to the presence of Fermi pockets formed by the states originating from the Nd block layer (BL).
In this talk, we show that more ideal d⁹ nickelates can be realized by adopting different types of BLs. By systematically generating new potential nickelate structures and then performing ab initio phonon calculations, we theoretically propose more than 10 new compounds that are dynamically stable and whose electronic structures better mimic that of the cuprates. We demonstrate that the newly proposed layered nickelates are in the strongly-correlated regime without forming an extra Fermi pocket as large as that of NdNiO₂. We also discuss the possibility of palladate analogues of high-Tc cuprates briefly. This presentation is based on Ref. [3].

[1] D. Li et al., Nature 572, 624 (2019).
[2] Y. Nomura et al., arXiv:1909.03942.
[3] M. Hirayama, T. Tadano, et al., arXiv:1910.03974.