Superconductivity and normal-state transport in compressively strained La$_2$PrNi$_2$O$_7$ thin films

TL;DR

This paper reports the discovery of intrinsic superconductivity in compressively strained La$_2$PrNi$_2$O$_7$ thin films with onset temperatures above 48 K, achieved through strain engineering and optimized growth techniques, revealing properties similar to overdoped cuprates.

Contribution

The study demonstrates intrinsic superconductivity in La$_2$PrNi$_2$O$_7$ thin films at high temperatures using strain and growth optimization, advancing the understanding of nickelate superconductors.

Findings

Superconductivity onset above 48 K in thin films.

Zero resistance achieved above 30 K.

Critical current density is 100 times larger than previous reports.

Abstract

The discovery of superconductivity under high pressure in Ruddlesden-Popper phases of bulk nickelates has sparked great interest in stabilizing ambient pressure superconductivity in thin-film form using epitaxial strain. Recently, signs of superconductivity have been observed in compressively strained bilayer nickelate thin films with an onset temperature exceeding 40 K, albeit with broad and two-step-like transitions. Here, we report intrinsic superconductivity and normal-state transport properties in compressively strained La$_2$PrNi$_2$O$_7$ thin films, achieved through a combination of isovalent Pr substitution, growth optimization, and precision ozone annealing. The superconducting onset occurs above 48 K, with zero resistance reached above 30 K, and the critical current density at 1.4 K is 100-fold larger than previous reports. The normal-state resistivity exhibits quadratic temperature dependence indicative of Fermi liquid behaviour, and other phenomenological similarities to transport in overdoped cuprates suggest parallels in their emergent properties.