Two-gap superconductivity in Ag1–x Mo6S8 Chevrel phase

The superconducting properties of Ag1−xMo6S8 [x = 0.08(1)] Chevrel phase [Tc = 7.9(5) K] are studied on a sample compacted by spark plasma sintering. Both lower [Bc1 = 12(1) mT] and the upper [Bc2(0) ~ 7.4(9) T] critical magnetic fields are obtained from magnetization and electrical resistivity measurements for the first time. The analysis of the low-temperature electronic specific heat indicates Ag1−xMo6S8 to be a two band superconductor with the energy gaps delta-1 = 1.6 meV (95 %) and delta-2 = 0.7 meV (5 %). Theoretical DFT calculations reveal a much stronger electron-phonon coupling in the studied Chevrel phase compared to earlier reports.