Correlation between superfluid density and transition temperature in infinite-layer nickelate superconductor $Nd_{1-x}Sr_xNiO_2$

TL;DR

This study investigates the local relationship between superfluid density and transition temperature in an infinite-layer nickelate superconductor, revealing a correlation similar to that in cuprates, despite sample inhomogeneity.

Contribution

It provides the first local-scale analysis of superfluid density and $T_c$ in nickelates, uncovering a linear and sub-linear dependence and suggesting a link to cuprate superconductors.

Findings

Linear dependence of $T_c$ on superfluid density for $T_c$>8 K

Sub-linear dependence for $T_c$<8 K

Similarity to overdoped cuprate superconductor behavior

Abstract

A strong correlation between zero-temperature superfluid density ($\rho_{s0}$) and transition temperature ($T_c$) is considered as a hallmark of unconventional superconductivity. However, their relationship has yet to be unveiled in nickelates due to sample inhomogeneity. Here we perform local susceptometry on an infinite-layer nickelate superconductor $Nd_{0.8}Sr_{0.2}NiO_2$. The sample shows inhomogeneous superfluid density and $T_c$ on micron-scale. The spatial statistics for different scan areas reveal a linear dependence of local $T_c$ on $\rho_{s0}$ for $T_c$>8 K and a sub-linear one for $T_c$<8 K. Remarkably, the overall relationship is reminiscent of that reported in overdoped cuprate superconductors, hinting at a close connection between them.