Magnetic Correlations and Pairing Tendencies of the Hybrid Stacking Nickelate Superlattice La$_7$Ni$_5$O$_{17}$ (La$_3$Ni$_2$O$_7$/La$_4$Ni$_3$O$_{10}$) under Pressure

TL;DR

This study investigates the magnetic correlations and potential superconducting pairing in the high-pressure phase of La7Ni5O17, revealing a dominant s± pairing state and antiferromagnetic fluctuations similar to known nickelate superconductors.

Contribution

It provides the first comprehensive analysis of the magnetic and pairing tendencies of La7Ni5O17 under pressure, highlighting its potential for high-temperature superconductivity.

Findings

High-pressure phase stabilizes a small hole pocket critical for superconductivity.

Predominant s± pairing state with pairing strength comparable to known nickelates.

Antiferromagnetic fluctuations drive the pairing, with decoupled middle trilayer.

Abstract

Motivated by the recent rapid progress in high-$T_c$ nickelate superconductors, we comprehensively study the physical properties of the alternating bilayer trilayer stacking nickelate La$_7$Ni$_5$O$_{17}$. The high-symmetry phase of this material, without the tilting of oxygen octahedra, is not stable at ambient conditions but becomes stable under high pressure, where a small hole pocket $\gamma_0$, composed of the $d_{3z^2-r^2}$ states in the trilayer sublattice, appears. This pocket was identified in our previous work for trilayer La$_4$Ni$_3$O$_{10}$ as important to develop superconductivity. Moreover, using random-phase approximation calculations, we find a leading $s^\pm$ pairing state for the high-symmetry phase under pressure with similar pairing strength as that obtained previously for the bilayer La$_3$Ni$_2$O$_7$ compound, suggesting a similar or higher superconducting transition temperature $T_c$. In addition, we find that the dominant magnetic fluctuations in the system driving this pairing state have antiferromagnetic structure both in-plane and between the planes of the top and bottom trilayer and bilayer sublattices, while the middle trilayer is magnetically decoupled.