Impact of spin–orbit coupling on physical properties and superconductivity in noncentrosymmetric superconductors Ru7B3 and Re7B3

Abstract

We have made a first-principles investigation of the effect of spin–orbit coupling (SOC) the physical properties and superconductivity of noncentrosymmetric hexagonal superconductors T7B3 (T = Ru and Re). In general, the influence of SOC on the electronic, elastic and mechanical properties is slightly larger for Re7B3 due to larger nuclear charge of Re as compared to that of Ru since the strength of this coupling varies as Z4 (Z is atomic number). For both compounds, the transition metal-related phonon modes form more than 90% of the electron–phonon coupling parameter. SOC is slightly more effective on the Eliashberg spectral function of Re7B3 than that of Ru7B3, increasing the electron–phonon coupling parameter for the former by around 3.0% and decreasing it by less than 1.0% for the latter. As a consequence, SOC increases the superconducting transition temperature of Re7B3 from 2.20 to 2.51 K and decreases that of Ru7B3 4.34 to 3.79 K. © 2023 Elsevier B.V.