Evolution of superconducting and transport properties in annealed FeTe1−xSex (0.1 ≤ x ≤ 0.4) multiband superconductors

We investigated the superconducting and transport properties in FeTeSex (0.1 x 0.4) single crystals prepared by O2-annealing. The sharp superconducting transition width observed in the magnetization measurement and the small residual resistivity prove the high quality of the crystals. All the crystals manifest large, homogeneous, and isotropic critical current density Jc with a self-field value over 105 A cm−2 at 2 K. The large and field-robust critical current densities prove that the superconductivity in FeTeSex (0.1 x 0.4) is in bulk nature. The values of anisotropy parameter close to Tc for crystals with different Se doping levels all reside in the range of 2–3. Hall coefficients RH remain positive and at an almost constant value at high temperatures, followed by a sudden decrease before reaching Tc, which indicates that the electron-type charge carriers become dominant at low temperatures. Furthermore, the characteristic temperature for the sudden decrease in RH gradually increases with Se doping.