Electronic structure, self-doping, and superconducting instability in the alternating single-layer trilayer stacking nickelates <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>La</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mi>Ni</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>7</mml:mn> </mml:msub> </mml:mrow> </mml:math>
Yang Zhang, Ling-Fang Lin, Adriana Moreo, Thomas Maier, Elbio Dagotto
Abstract
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 ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$-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.