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Arsenic doping in silicides has been much less studied compared with phosphorus. In this study, superconductivity is successfully induced by As doping in Mo$_5$Si$_3$. The superconducting transition temperature ($T_c$) reaches 7.7 K, which is higher than those in previously known W$_5$Si$_3$-type superconductors. Mo$_5$Si$_2$As is a type-II BCS superconductor with upper and lower critical fields of 6.65 T and 22.4 mT, respectively. In addition, As atoms are found to selectively take the 8$h$ sites in Mo$_5$Si$_2$As. The emergence of superconductivity is possibly due to the shift of Fermi level as a consequence of As doping, as revealed by the specific heat measurements and first-principles calculations. Our work provides not only another example of As doping, but also a practical strategy to achieve superconductivity in silicides through Fermi level engineering., Comment: Supporting Information available at the corresponding DOI

Arsenic doping in silicides has been much less studied compared with phosphorus. In this study, superconductivity is successfully induced by As doping in Mo

We report the discovery and detailed investigation of superconductivity in Mo4Ga20As. Mo4Ga20As crystallizes in a space group of I4/m (No. 87), with the lattice parameters a = 12.86352 Å and c = 5.30031 Å. The resistivity, magnetization, and specific heat data reveal Mo4Ga20As to be a type-II superconductor with T c = 5.6 K. The upper and lower critical fields are estimated to be 2.78 T and 22.0 mT, respectively. In addition, electron-phonon coupling in Mo4Ga20As is possibly stronger than the BCS weak-coupling limit. First-principles calculations suggest the Fermi level being dominated by the Mo-4d and Ga-4p orbitals.

By performing P doping on the Si sites in the topological semimetal Mo$_5$Si$_3$, we discover strong-coupling superconductivity in Mo$_5$Si$_{3-x}$P$_x$ (0.5 $\le$ $x$ $\le$ 2.0). Mo$_5$Si$_3$ crystallizes in the W$_5$Si$_3$-type structure with space group of $I4/mcm$ (No. 140), and is not a superconductor itself. Upon P doping, the lattice parameter $a$ decreases while $c$ increases monotonously. Bulk superconductivity is revealed in Mo$_5$Si$_{3-x}$P$_x$ (0.5 $\le$ $x$ $\le$ 2.0) from resistivity, magnetization, and heat capacity measurements. $T_c$ in Mo$_5$Si$_{1.5}$P$_{1.5}$ reaches as high as 10.8 K, setting a new record among the W$_5$Si$_3$-type superconductors. The upper and lower critical fields for Mo$_5$Si$_{1.5}$P$_{1.5}$ are 14.56 T and 105 mT, respectively. Moreover, Mo$_5$Si$_{1.5}$P$_{1.5}$ is found to be a fully gapped superconductor with strong electron-phonon coupling. First-principles calculations suggest that the enhancement of electron-phonon coupling is possibly due to the shift of the Fermi level, which is induced by electron doping. The calculations also reveal the nontrivial band topology in Mo$_5$Si$_3$. The $T_c$ and upper critical field in Mo$_5$Si$_{3-x}$P$_x$ are fairly high among pseudobinary compounds. Both of them are higher than those in NbTi, making future applications promising. Our results suggest that the W$_5$Si$_3$-type compounds are ideal platforms to search for new superconductors. By examinations of their band topologies, more candidates for topological superconductors can be expected in this structural family., Comment: 15 pages, 5 figures. Supplementary Information availabe at the corresponding DOI

We report systematic studies on superconducting properties of the Laves phase superconductor ZrIr2. It crystallizes in a C15-type (cubic MgCu2-type, space group F d 3 ¯ m ) structure in which the Ir atoms form a kagome lattice, with cell parameters a = b = c = 7.3596(1) Å. Resistivity and magnetic susceptibility measurements indicate that ZrIr2 is a type-II superconductor with a transition temperature of 4.0 K. The estimated lower and upper critical fields are 12.8 mT and 4.78 T, respectively. Heat capacity measurements confirm the bulk superconductivity in ZrIr2. ZrIr2 is found to possibly host strong-coupled s-wave superconductivity with the normalized specific heat change ΔC e/γ T c ∼ 1.86 and the coupling strength Δ0/k B T c ∼ 1.92. First-principles calculations suggest that ZrIr2 has three-dimensional Fermi surfaces with simple topologies, and the states at Fermi level mainly originate from the Ir-5d and Zr-4d orbitals. Similar to SrIr2 and ThIr2, spin–orbit coupling has dramatic influences on the band structure in ZrIr2.