The Superconductivity in Bi-Doped BaFeAs Single Crystals.

We have successfully synthesized a series of Bi-doped BaFeAs high-quality single crystals for the first time. X-ray diffraction (XRD) patterns show an expansion of lattice parameter with Bi doping, indicating a negative pressure effect. By investigating the resistivity, a Fermi liquid (FL) to non-Fermi liquid (NFL) crossover is observed from normal state to antiferromagnetic order state, accompanied by three superconducting transitions labeled as SC I, SC II and SC III, which are supposed to be induced by three superconducting realms with various Bi concentrations.