Structural transition and possible pressure-induced superconductivity in a suboxide La$_5$Pb$_3$O

TL;DR

This study investigates a structural phase transition in La$_5$Pb$_3$O and its potential to induce superconductivity under pressure, revealing a transition at 225 K and superconductivity up to 10 K with pressure application.

Contribution

The paper reports the discovery of a pressure-tunable structural transition and possible superconductivity in La$_5$Pb$_3$O, highlighting the interplay between structural changes and superconductivity.

Findings

Structural transition at 225 K from I4/mcm to P4/ncc

Suppression of the transition and emergence of superconductivity under pressure

No significant change in electronic density of states across the transition

Abstract

Here we report a structural phase transition and its possible competition with superconductivity in the suboxide La$_5$Pb$_3$O. Upon cooling through $T_t$ = 225 K, La$_5$Pb$_3$O transforms from a high-temperature I4/mcm to a low-temperature P4/ncc structure in which La - Pb dimerization along the c-axis occurs. This transition is accompanied by anomalies in the temperature dependence of electrical resistivity and specific heat. High-pressure electrical transport measurements reveal that hydrostatic pressure suppresses the structural transition and possibly induces superconductivity with a maximum superconducting temperature of 10 K. Density functional theory calculations show minimal changes in the electronic density of states and no gap opening at $E_F$ across $T_t$, suggesting that the transition is driven by bonding effects rather than Fermi surface instability. These findings establish La$_5$Pb$_3$O as a promising platform for exploring the interplay between weak structural transitions and superconductivity.