High-temperature superconductivity with zero-resistance and strange metal behavior in La$_{3}$Ni$_{2}$O$_{7-\delta}$

TL;DR

This study demonstrates zero resistance in La$_{3}$Ni$_{2}$O$_{7- ext{delta}}$ under high pressure, revealing its high-temperature superconductivity and its connection to strange metal behavior, akin to other unconventional superconductors.

Contribution

First demonstration of zero resistance in La$_{3}$Ni$_{2}$O$_{7- ext{delta}}$ under pressure, establishing its high-temperature superconductivity and linking strange metal behavior to superconductivity.

Findings

La$_{3}$Ni$_{2}$O$_{7- ext{delta}}$ exhibits zero resistance under pressure.

The material remains metallic without a metal-insulator transition.

Strange metal behavior correlates with superconductivity and is suppressed by pressure.

Abstract

Recently signatures of superconductivity were observed close to 80 K in \LN\ under pressure. This discovery positions \LN\ as the first bulk nickelate with high-temperature superconductivity, but the lack of zero resistance presents a significant drawback for validating the findings. Here we report pressure measurements up to over 30 GPa using a liquid pressure medium and show that single crystals of \LNO\ do exhibit zero resistance. We find that \LNO\ remains metallic under applied pressures, suggesting the absence of a metal-insulator transition proximate to the superconductivity. Analysis of the normal state $T$-linear resistance suggests an intricate link between this strange metal behaviour and superconductivity, whereby at high pressures both the linear resistance coefficient and superconducting transition are slowly suppressed by pressure, while at intermediate pressures both the superconductivity and strange metal behaviour appear disrupted, possibly due to a nearby structural instability. The association between strange metal behaviour and high-temperature superconductivity is very much in line with diverse classes of unconventional superconductors, including the cuprates and Fe-based superconductors. Understanding the superconductivity of \LNO\ evidently requires further revealing the interplay of strange metal behaviour, superconductivity, as well as possible competing electronic or structural phases.