Endohedral Cluster Superconductors in the Mo-Ga-Sn System Explored by the Joint Flux Technique

Valeriy Yu Verchenko; Alexander O Zubtsovskii; Zheng Wei; Alexander A Tsirlin; Miroslav Marcin; Alexey V Sobolev; Igor A Presniakov; Evgeny V Dikarev; Andrei V Shevelkov

doi:10.1021/acs.inorgchem.9b02598

Endohedral Cluster Superconductors in the Mo-Ga-Sn System Explored by the Joint Flux Technique

Inorg Chem. 2019 Nov 18;58(22):15552-15561. doi: 10.1021/acs.inorgchem.9b02598. Epub 2019 Oct 28.

Authors

Affiliations

¹ Department of Chemistry , Lomonosov Moscow State University , 119991 Moscow , Russia.
² National Institute of Chemical Physics and Biophysics , 12618 Tallinn , Estonia.
³ Experimental Physics VI, Center for Electronic Correlations and Magnetism, Institute of Physics , University of Augsburg , 86135 Augsburg , Germany.
⁴ Department of Chemistry , University at Albany, SUNY , Albany New York 12222 , United States.
⁵ Institute of Experimental Physics , Slovak Academy of Sciences , 04001 Košice , Slovakia.

PMID: 31657910
DOI: 10.1021/acs.inorgchem.9b02598

Abstract

Endohedral Ga cluster compounds feature nontrivial superconducting states including the two-gap superconductivity similar in nature to MgB₂. 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 Mo₈Ga_41-xSn_x and Mo₄Ga_21-x-δSn_x with critical temperatures of T_c = 8.7 and 5.85 K, respectively. While the former compound is a derivative of the previously known Mo₈Ga₄₁ superconductor, where Sn atoms are enclosed inside the Sn@Ga₆ octahedral clusters, the latter is a new architecture built upon Mo@Ga₉Sn clusters, Ga@Ga₁₂ cuboctahedra, and Sn₄ squares. We show that this novel Mo₄Ga_21-x-δSn_x superconductor features strong electron-phonon coupling with the large ratio of 2Δ(0)/(k_BT_c) = 4.1 similar to that of the Mo₈Ga₄₁ superconductor with the closely related crystal structure.