Pressure Study of BiS₂-Based Superconductors Bi₄O₄S₃and La(O,F)BiS₂

Abstract

We report the electrical resistivity measurements under pressure for the\nrecently discovered BiS2-based layered superconductors Bi4O4S3 and La(O,F)BiS2.\nIn Bi4O4S3, the transition temperature Tc decreases monotonically without a\ndistinct change in the metallic behavior in the normal state. In La(O,F)BiS2,\non the other hand, Tc initially increases with increasing pressure and then\ndecreases above ? 1 GPa. The semiconducting behavior in the normal state is\nsuppressed markedly and monotonically, whereas the evolution of Tc is\nnonlinear. The strong suppression of the semiconducting behavior without doping\nin La(O,F)BiS2 suggests that the Fermi surface is located in the vicinity of\nsome instability. In the present study, we elucidate that the superconductivity\nin the BiS2 layer favors the Fermi surface at the boundary between the\nsemiconducting and metallic behaviors.\n