Crystal growth and characterization of a hole-doped iron-based superconductor Ba(Fe_0.875Ti_0.125)₂As₂

We report the crystal growth of a new hole-doped iron-based superconductor Ba(Fe_0.875Ti_0.125)₂As₂ by substituting Ti on the Fe site. The crystals are accidentally obtained in trying to grow Ni doped Ba₂Ti₂Fe₂As₄O. After annealing at 500 °C in vacuum for one week, superconductivity is observed with zero resistance at T_c0 ≈ 17.5 K, and about 20% diamagnetic volume down to 2 K. While both the small anisotropy of superconductivity and the temperature dependence of normal state resistivity are akin to the electron doped 122-type compounds, the Hall coefficient is positive and similar to the case in hole-doped Ba_0.9K_0.1Fe₂As₂. The density functional theory calculations suggest dominated hole pockets contributed by Fe/Ti 3d orbitals. Therefore, the Ba(Fe_1−xTi_x)₂As₂ system provides a new platform to study the superconductivity with hole doping on the Fe site of iron-based superconductors.