Inorganic Chemistry · 2019 · 13 citations · 24 references
Endohedral Ga cluster compounds feature nontrivial superconducting states including the two-gap superconductivity similar in nature to MgB<sub>2</sub>. We use the joint flux synthetic technique to introduce Sn into the Ga matrix and tune the valence electron count in the two new endohedral cluster superconductors Mo<sub>8</sub>Ga<sub>41-<i>x</i></sub>Sn<sub><i>x</i></sub> and Mo<sub>4</sub>Ga<sub>21-<i>x</i>-δ</sub>Sn<sub><i>x</i></sub> with critical temperatures of <i>T</i><sub>c</sub> = 8.7 and 5.85 K, respectively. While the former compound is a derivative of the previously known Mo<sub>8</sub>Ga<sub>41</sub> superconductor, where Sn atoms are enclosed inside the Sn@Ga<sub>6</sub> octahedral clusters, the latter is a new architecture built upon Mo@Ga<sub>9</sub>Sn clusters, Ga@Ga<sub>12</sub> cuboctahedra, and Sn<sub>4</sub> squares. We show that this novel Mo<sub>4</sub>Ga<sub>21-<i>x</i>-δ</sub>Sn<sub><i>x</i></sub> superconductor features strong electron-phonon coupling with the large ratio of 2Δ(0)/(<i>k</i><sub>B</sub><i>T</i><sub>c</sub>) = 4.1 similar to that of the Mo<sub>8</sub>Ga<sub>41</sub> superconductor with the closely related crystal structure.
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