Impact of Pressure and Apical Oxygen Vacancies on Superconductivity in La$_3$Ni$_2$O$_7$

TL;DR

This study explores how pressure and apical oxygen vacancies influence superconductivity in La$_3$Ni$_2$O$_7$, revealing that pressure enhances pairing while oxygen vacancies suppress it, offering insights for optimizing high-$T_c$ superconductivity.

Contribution

It introduces a theoretical model analyzing the effects of pressure-induced structural changes and oxygen vacancies on superconductivity in La$_3$Ni$_2$O$_7$, highlighting key factors for tuning its properties.

Findings

High pressure enhances pairing strength in La$_3$Ni$_2$O$_7$.

Oxygen vacancies suppress pairing and superfluid density.

Structural phase transition under pressure affects superconductivity.

Abstract

The bilayer nickelate La$_3$Ni$_2$O$_7$ under pressure has recently emerged as a promising system for high-$T_c$ superconductivity. In this work, we investigate the fate of the superconducting properties in La$_3$Ni$_2$O$_{7}$ under pressure, focusing on the effects of structural deformation and apical oxygen vacancies. Employing a low-energy effective $t$-$J_{\parallel}$-$J_{\perp}$ model for the $3d_{x^2-y^2}$ orbitals within the slave-boson mean-field approach, we demonstrate that the pairing strength is significantly enhanced in the high-pressure tetragonal $I4/mmm$ phase compared to the ambient pressure orthorhombic $Amam$ phase. Furthermore, by simulating random configurations of apical oxygen vacancies, we show that oxygen vacancies suppress both pairing strength and superfluid density. These results underscore the critical role of pressure and oxygen stoichiometry in tuning the SC of La$_3$Ni$_2$O$_7$, providing key insights into optimizing its high-$T_c$ behavior.