Opposite-Mirror-Parity Scattering as the Origin of Superconductivity in Strained Bilayer Nickelates

TL;DR

This paper investigates the origin of superconductivity in strained bilayer nickelates, revealing that opposite-mirror-parity Fermi surface scattering and strain conditions critically influence pairing mechanisms and superconducting states.

Contribution

It introduces a microscopic scenario linking mirror parity scattering and strain effects to superconductivity in nickelates, advancing understanding of high-Tc pairing in correlated materials.

Findings

Superconductivity emerges from interlayer pairing reinforced by spin fluctuations.

Strain modulates superconductivity, with compression favoring and tension suppressing pairing.

Fermi surface scattering between opposite mirror parity electrons governs ordering tendencies.

Abstract

We study the electronic structure and doping-dependent instabilities of strained La$_3$Ni$_2$O$_7$ thin films using first-principles and functional renormalization group methods. We demonstrate that ordering tendencies are governed by Fermi surface scattering between electrons of opposite mirror parity. Under moderate hole doping, when the $d_{z^2}$ bonding band becomes incipient or crosses the Fermi level, robust $s_{\pm}$-wave superconductivity emerges from cooperative interlayer pairing reinforced by two competing spin-density-wave fluctuations. Compressive strain favors superconductivity in NiO$_2$ bilayers slightly away from the interface, whereas tensile strain induces pair-breaking nesting that suppresses pairing. Our results establish a unified microscopic scenario for superconductivity in pressurized bulk and strained thin-film nickelates, providing new insights into high-T$_c$ pairing in correlated quantum materials.