Magnetic penetration depth and $T_c$ in superconducting nickelates

TL;DR

This paper calculates the magnetic penetration depth in nickelate superconductors from first principles and compares it to their critical temperature, revealing discrepancies with cuprate phenomenology and estimating a potential maximum $T_c$ of about 180 K.

Contribution

It provides first-principles calculations of magnetic penetration depth in nickelates and analyzes their relation to $T_c$, challenging existing cuprate-based correlations.

Findings

Discrepancy with cuprate Uemura plot observed.

Estimated maximum $T_c$ around 180 K in ultrathin limit.

First-principles approach applied to nickelate superconductors.

Abstract

We compute the nominal magnetic penetration depth of $R$NiO$_2$ ($R =$ La, Nd) from first principles calculations and discuss the results in relation to the superconducting $T_c$. We find a marked discrepancy with the well established phenomenology that correlates these two quantities in cuprates (Uemura plot). We also consider the 2D ultrathin limit and estimate the maximum attainable $T_c$ to be $\sim 180$ K according to the Nelson-Kosterliz universal relation between the superfluid density and the transition temperature.