Mechanism of superconductivity and Tc trend in Sc6MTe2 (M = Fe, Co, Ni)

Determine the mechanism responsible for the occurrence of superconductivity in Sc6MTe2 compounds that include magnetic transition-metal elements (M = Fe, Co, Ni), and ascertain why the superconducting transition temperature is highest in Sc6FeTe2 and lowest in Sc6NiTe2.

Background

Sc6MTe2 (M = Fe, Co, Ni) forms part of a family of d-element-rich compounds recently reported to exhibit bulk superconductivity with distinct Tc values across Fe, Co, and Ni. Although superconductivity is well established experimentally in these materials, the microscopic pairing mechanism and the chemical trend of Tc remain unsettled, particularly given the presence of magnetic elements.

The paper undertakes an ab initio investigation of electronic structure, phonon properties, and electron-phonon coupling to address these uncertainties. The explicit open question is framed in the Introduction prior to presenting the computational approach and results that aim to clarify the role of charge transfer, suppression of magnetism, and low-frequency rattling phonons.