Superconductivity at Tc ∼14 K in single-crystalline FeTe_0.61 Se_0.39

Single-crystalline FeTe_0.61 Se_0.39 with a sharp superconducting transition at Tc ∼14 K is synthesized via slow furnace cooling followed by low-temperature annealing. The effect of annealing on the chemical and superconducting inhomogeneities is carefully characterized. We also report resistivity, magnetization, and magneto-optical images of this crystal. Based on the Bean model, critical current density is estimated to exceed 1× 105 A/ cm2 below 5 K under zero field. Weak fish-tail effect is identified at lower temperatures.