Electronic structure and Pairing Tendencies of the Hybrid Stacking Nickelate Superlattice

Recently, an alternating single-layer (SL) / trilayer (TL) stacking structure was proposed in experiments to have the same chemical formula La₃Ni₂O₇ as the bilayer stacking high-Tc superconductors. Here, our analysis unveils similarities between these novel structures and other nickelate superconductors, such as a similar charge-transfer gap value and orbital-selective behavior of the e_g orbitals. In addition, we observe a “self-doping” effect from the TL to the SL sublattices and this effect will be enhanced by overall electron doping. Moreover, we find a leading dx²−y²-wave pairing state that is restricted to the single layer. Because the effective coupling between the single layers is very weak, due to the nonsuperconducting trilayer in-between, this suggests that the observed high Tc does not originate from the SL-TL stacking structure [1]. Futhermore, we also investigated the BL-TL stacking nickelate superlattice La₇Ni₅O₁₇. Similar to other nickelate superconductors, the high-symmetry phase without the tilting of oxygen octahedra, is not stable at 0 GPa but becomes stable under high pressure. Moreover, we also find a leading s± pairing state for the high-symmetry phase under pressure with similar pairing strength as that obtained previously for the BL La₃Ni₂O₇ compound, suggesting a similar or higher superconducting transition temperature T_c [2].