Motivated by the recently proposed alternating single-layer trilayer stacking structure for the nickelate ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$, we comprehensively study this system using ab initio and random-phase approximation techniques. Our analysis unveils similarities between this novel ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ structure and other Ruddlesden-Popper nickelate superconductors, such as a similar charge-transfer gap value and orbital-selective behavior of the $e_g$ orbitals. Pressure primarily increases the bandwidths of the Ni $e_g$ bands, suggesting an enhancement of the itinerant properties of those $e_g$ states. By changing the cell volume ratio $V/V_0$ from 0.9 to 1.10, we found that the bilayer structure in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ always has lower energy than the single-layer trilayer stacking ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$. In addition, we observe a “self-doping” effect (compared to the average 1.5 electrons per $e_g$ orbital per site of the entire structure) from the trilayer to the single-layer sublattices and this effect will be enhanced by overall electron doping. Moreover, we find a leading $d_{x^2-y^2}$-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 superconducting transition temperature $T_c$ in this structure should be much lower than in the bilayer structure.

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• Multiband superconductivity
• Pairing mechanisms
• Superconductivity
• High-temperature superconductors
• Nickelates
• Electron-correlation calculations
• First-principles calculations
• Hubbard model
• Random phase approximation
• Wannier function methods