Anomalous Transport Properties in BiS2-based Superconductors LnO(1-x),FxBiS2 (Ln = Nd, La-Sm)

摘要

We report the electronic properties of the layered bismuth-based sulfide superconductors NdO1-xFxBiS2 (x = 0.25, 0.4, and 0.5) and La1-ySmyO0.5F0.5BiS2 (y = 0.1-0.7), which have been studied by investigation of their transport properties and X-ray diffraction. In the lightly carrier-doped NdO1-xFxBiS2 (x = 0.25 and 0.4) and La1-ySmyO0.5F0.5BiS2 (y = 0.3 and 0.4), the resistivity and Hall coefficient exhibit anomalous temperature dependences below T-CDW( )similar to 130 and 200 K, respectively, suggesting the formation of an energy gap on the Fermi surface associated with charge-density wave (CDW). In NdO1-xFxBiS2 (x = 0.25), the bond angles and bond lengths of the Bi-S pentahedron change their temperature dependences below similar to 200K, suggesting that a lattice instability related to the Bi-S pentahedron exists below similar to 200K, which is much higher than T-CDW. These results indicate that the lattice instability of the Bi-S pentahedron can trigger a CDW transition in the low-carrier region of BiS2 superconductors.