Superconducting properties of the C15-type Laves phase ZrIr2 with an Ir-based kagome lattice

We report systematic studies on superconducting properties of the Laves phase superconductor ZrIr 2 . It crystallizes in a C15-type (cubic MgCu 2 -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 ZrIr 2 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 ZrIr 2 . ZrIr 2 is found to possibly host strong-coupled s-wave superconductivity with the normalized specific heat change Δ C e / γ T c ∼ 1.86 and the coupling strength Δ 0 / k B T c ∼ 1.92. First-principles calculations suggest that ZrIr 2 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 SrIr 2 and ThIr 2 , spin–orbit coupling has dramatic influences on the band structure in ZrIr 2 .