Enhanced $s^\pm$-wave superconductivity in electron-doped La$_3$Ni$_2$O$_7$

TL;DR

This study predicts that electron doping enhances $s^$-wave superconductivity in LaNiO$ through first-principles and quantum Monte Carlo methods, especially in heterostructures, suggesting new avenues for experimental exploration.

Contribution

It provides the first systematic theoretical investigation of electron doping effects on superconductivity in LaNiO, highlighting an inter-orbital cooperative pairing mechanism.

Findings

Electron doping enhances $s^$-wave pairing in LaNiO$.

Heterostructures show the highest $T_c$ in the underdoped regime.

Inter-orbital pairing mechanism is crucial for superconductivity.

Abstract

In cuprates, electron doping yields a much lower superconducting $T_c$ than hole doping. For recently discovered nickelate superconductors, the analogous doping strategies become more challenging. Consequently, while hole-doped Ruddlesden-Popper (RP) nickelates have been extensively studied, electron-doped RP nickelates remain rarely explored both experimentally and theoretically. Here we fill this gap by systematically investigating the two-orbital bilayer model for three representative systems: bulk La$_3$Ni$_2$O$_7$ at ambient pressure and 15\,GPa, and a heterostructure La$_3$Ni$_2$O$_7$:La$_3$Al$_2$O$_7$ that provides a feasible experimental route to electron doping. Using first-principle calculations and large-scale dynamical cluster quantum Monte Carlo simulations, we find that electron doping generically enhances $s^\pm$-wave pairing superconductivity (SC) in all three cases, with the heterostructure showing the highest $T_c$ in the underdoped regime. Furthermore, our results suggest an inter-orbital cooperative mechanism that the pairing on the $d_{x^2-y^2}$ orbital, induced by that on the $d_{z^2}$ orbital, plays a vital role in the SC. This work provides the theoretical prediction of enhanced SC in electron-doped RP nickelates and calls for future experimental verification.