Divergent Pressure Response of Superconductivity in Sc$_{6}$MTe$_{2}$ ($M$ = Fe, Ru and Ir)

TL;DR

This study investigates how hydrostatic pressure differently affects superconductivity in the isostructural Sc6MTe2 series, revealing contrasting behaviors linked to the electronic nature of the transition metal M.

Contribution

It provides the first systematic comparison of pressure effects on superconductivity across 3d, 4d, and 5d transition metal-based compounds in the same structural family.

Findings

$T_{C}$ decreases under pressure for Fe-based compound.

$T_{C}$ increases under pressure for Ru- and Ir-based compounds.

Ru compound shows nearly 50% increase in $T_{C}$ within 2 GPa.

Abstract

Identifying and understanding non-BCS superconductivity remains a central challenge in condensed-matter physics. Here we focus on the Sc$_{6}$MTe$_{2}$ family (M =d-electron metal), which provides a unique platform of isostructural compounds exhibiting superconductivity across 3d, 4d, and 5d systems. Using hydrostatic pressure as an additional tuning parameter, muon-spin rotation (${\mu}$SR) and AC susceptibility measurements uncover strongly contrasting pressure responses of superconductivity across the Sc$_{6}$MTe$_{2}$ series. The superconducting transition temperature, $T_{\rm C}$ decreases under pressure in the 3d Fe-based compound but increases for the 4d Ru- and 5d Ir-based systems, with the Ru compound showing the largest enhancement of nearly 50% within 2 GPa. The superfluid density exhibits similarly distinct pressure dependences, remaining nearly pressure independent for Fe while decreasing with increasing pressure for Ru and Ir. This suggests fundamentally different correlations between $T_{\rm C}$ and the superfluid density. Together, these results indicate that superconductivity emerging from strongly correlated and spin-orbit-dominated regimes in Sc$_{6}$MTe$_{2}$ is likely governed by different microscopic mechanisms and offer a useful experimental basis for future microscopic theoretical studies.