Phase Diagram of Infinite Layer Praseodymium Nickelate Pr$_{1-x}$Sr$_{x}$NiO$_2$ Thin Films

TL;DR

This study maps the phase diagram of Pr$_{1-x}$Sr$_{x}$NiO$_2$ thin films, revealing a doping-dependent superconducting dome with a maximum $T_c$ of 14 K, and compares it to Nd-based nickelates, highlighting similarities and differences.

Contribution

It provides the first detailed phase diagram of Pr-based nickelates, showing their superconducting behavior and comparing it with Nd-based counterparts, emphasizing the role of rare-earth elements.

Findings

Superconducting dome extends between x=0.12 and 0.28.

Maximum $T_c$ of 14 K at x=0.18.

Hall effect shows mixed carriers and sign change.

Abstract

We report the phase diagram of infinite layer Pr$_{1-x}$Sr$_{x}$NiO$_2$ thin films synthesized via topotactic reduction from the perovskite precursor phase using CaH$_2$. Based on the electrical transport properties, we find a doping-dependent superconducting dome extending between $x$ = 0.12 and 0.28, with a maximum superconducting transition temperature $T_{\rm{c}}$ of 14 K at $x$ = 0.18, bounded by weakly insulating behavior on both sides. In contrast to the narrower dome observed in Nd$_{1-x}$Sr$_{x}$NiO$_2$, a local $T_{\rm{c}}$ suppression near $x$ = 0.2 was not observed for the Pr$_{1-x}$Sr$_{x}$NiO$_2$ system. Normal state Hall effect measurements indicate mixed carrier contributions of both electrons and holes, and show a sign change in the Hall coefficient as functions of temperature and $x$, quite similar to that in Nd$_{1-x}$Sr$_{x}$NiO$_2$. Also similar is the observation of a minimum in the normal state resistivity associated with the superconducting compositions. These findings indicate an infinite layer nickelate phase diagram that is relatively insensitive to the rare-earth element, but suggest that disorder arising from the variations of the ionic radii on the rare-earth site affects the superconducting dome.