Superconductivity in Sc MTe Achieves 50% Enhancement Via Applied Pressure

Scientists are increasingly focused on understanding superconductivity beyond conventional theories, and new research published today sheds light on this complex phenomenon in a fascinating family of materials. J. N. Graham, S. S. Islam, and K. Yuchi, from their respective institutions, alongside P. Král, O. Gerguri, and S. Huber et al., investigated the behaviour of Sc MTe compounds (where M represents d-electron metals like iron, ruthenium, and iridium) under extreme pressure. Their work reveals a surprising divergence in how superconductivity responds to pressure , decreasing in the iron-based material, but increasing in those containing ruthenium and iridium, with the ruthenium compound exhibiting a remarkable 50% enhancement within just 2 GPa. This contrasting behaviour, evidenced through muon-spin rotation and AC susceptibility measurements, suggests fundamentally different mechanisms driving superconductivity in these materials and provides crucial experimental data to guide future theoretical investigations into strongly correlated electron systems.

Employing muon-spin rotation (μSR) and AC susceptibility measurements, the team achieved a detailed characterisation of the superconducting transition temperature (Tc) and superfluid density under varying pressure conditions, revealing a complex interplay between electronic correlations and spin-orbit coupling. The study establishes that the superconducting transition temperature decreases under pressure in the 3d Fe-based compound, but remarkably increases for both the 4d Ru- and 5d Ir-based systems, with the ruthenium compound exhibiting the most substantial enhancement, nearly 50% within just 2 GPa.

Experiments show that the superfluid density also displays distinct pressure dependences, remaining nearly pressure independent for the iron compound, while decreasing with increasing pressure for ruthenium and iridium. This suggests fundamentally different correlations between Tc and the superfluid density, indicating that the mechanisms driving superconductivity in these materials are not uniform. This systematic investigation across isostructural compounds provides crucial insights into manipulating physical characteristics through chemical composition and external tuning parameters like pressure.
Furthermore, the work opens new avenues for designing materials with tailored superconducting properties, as understanding how to balance electron correlations, lattice effects, and spin-orbit coupling is paramount for achieving unconventional superconductivity. Initial findings suggest that the higher Tc observed in the iron compound may be linked to strong electron-phonon coupling, while the ruthenium and iridium compounds exhibit exceptionally long London penetration depths, hinting at unconventional pairing mechanisms beyond the standard Bardeen-Cooper-Schrieffer (BCS) theory. Experiments revealed that the superconducting transition temperature (Tc) decreases under pressure in the 3d Fe-based compound, but notably increases for the 4d Ru- and 5d Ir-based systems. The Ru compound exhibited the most significant enhancement, with Tc increasing by nearly 50% within just 2 GPa.

Data shows the superfluid density also displays distinct pressure dependences; it remained nearly pressure independent for the Fe compound, while decreasing with increasing pressure for both Ru and Ir. Measurements confirm these differing behaviours suggest fundamentally different correlations between Tc and the superfluid density across the series. The team meticulously recorded Tc values and superfluid densities to establish these relationships, providing a detailed picture of how pressure influences superconductivity in these materials. Results demonstrate that the Sc6RuTe2 compound experiences a substantial rise in its superconducting properties under pressure.