Direct evidence of multi-band superconductivity in Mo₈Ga₄₁

Mo₈Ga₄₁, a member of the family of endohedral gallide cluster compounds shows superconductivity with relatively large Tc of 9.8 K as compare to the other members in this family. In order to study the superconducting phase of Mo₈Ga₄₁ a number of experiments have been employed and it was shown that this compound manifests unusually high electron-phonon coupling leading to a large △/k_BT_c ratio and an indication of multi-gap superconductivity was also found. In this talk, from the direct measurement of the superconducting energy gap measured by Scanning Tunneling Spectroscopy (STS), I will show that Mo₈Ga₄₁ is a two-gap superconductor like MgB₂ with the superconducting energy gaps of magnitude 0.85 meV and 1.6 meV respectively. Evolution of superconducting energy gaps with temperature and magnetic field demonstrates the conventional nature of both of the gaps as per the BCS prediction. In addition, through the band structure calculations, we have also identified the bands responsible for the two respective gaps and also shows that only two specific Mo sites in an unit cell contribute to superconductivity. Magnetic field dependent STS experiments further suggest that the interband coupling is weak in Mo₈Ga₄₁, as in case of MgB₂.