Superconducting properties of the spin Hall candidates Ti₃Ir and Ti₃Pt

Materials with A15 structure are emerging as a novel platform for realizing new phenomena resulting from the interplay of superconductivity, band topology and spin dynamics. Here, we present a study of the superconducting properties of the spin Hall candidate Ti₃Ir, an A15 compound, and its homolog Ti₃Pt. Bulk measurements including electrical resistivity, magnetic susceptibility and specific heat on Ti₃Ir show two clear anomalies: a superconducting transition at T_c ~ 4.5 K, and an anomaly at higher temperature T* ~ 90 K. Ti₃Pt has a superconducting T_c ~ 0.8 K but does not display an anomaly at temperatures above T_c. We attribute the high temperature transition in Ti₃Ir to crystal symmetry breaking resulting in a possible martensitic transition and charge density wave (CDW) formation. Via multiple techniques, we determine a superconducting phase diagram for each material and find large Ginzburg-Landau parameters, identifying both materials as extreme type-II. London penetration depth measurements at ³He temperatures on Ti₃Ir are consistent with a full BCS-like superconducting gap.