Superconductivity and Charge Density Wave in Iodine-Doped CuIr_2Te_4

We report a systematic investigation on the evolution of the structural and physical properties, including the charge density wave (CDW) and superconductivity of the polycrystalline CuIr_2Te_4- xI_x for 0.0 \le x \le 1.0. X-ray diffraction results indicate that both of a and c lattice parameters increase linearly when 0.0 \le x \le 1.0. The resistivity measurements indicate that the CDW is destabilized with slight x but reappears at x \ge 0.9 with very high T_\rm CDW. Meanwhile, the superconducting transition temperature T_\rm c enhances as x increases and reaches a maximum value of around 2.95 K for the optimal composition CuIr_2Te_1.9I_0.1 followed by a slight decrease with higher iodine doping content. The specific heat jump (\Delta C/\gamma T_\rm c) for the optimal composition CuIr_2Te_3.9I_0.1 is approximately 1.46, which is close to the Bardeen–Cooper–Schrieffer value of 1.43, indicating that it is a bulk superconductor. The results of thermodynamic heat capacity measurements under different magnetic fields C_\rm p(T, H), magnetization M(T, H) and magneto-transport \rho (T, H) measurements further suggest that CuIr_2Te_4- xI_x bulks are type-II superconductors. Finally, an electronic phase diagram for this CuIr_2Te_4- xI_x system has been constructed. The present study provides a suitable material platform for further investigation of the interplay of the CDW and superconductivity.