Growth and Characterizations of Iron-based Superconductor (Ba_1-xRb_x) Fe₂As₂ Single Crystals

Novel nematic states as well as remarkable superconducting properties were reported in iron-based superconductors. We synthesized high-quality single crystals of (Ba_1-xRb_x)Fe₂As₂ close to the optimal composition of x ≈ 0.4, and have characterized normal state and superconducting properties for pristine and proton irradiated samples. The highest T_c was found to be ∼36.6 K for pristine samples. A maximum critical current density of 12 MA/cm² was achieved in a proton irradiated sample, which is comparable to that in irradiated (Ba_0.6K_0.4) Fe₂As₂. Twin boundaries were observed optically in both non-doped and under-doped samples. We also attempted local magnetic field measurements induced by transport current in a sample with twin boundaries for future exploration of nematic states in different regions of doping. (paper)