Superconductivity appears in the vicinity of semiconducting-like behavior in CeO1−xFxBiS2

Abstract

Resistive and magnetic properties have been measured in BiS${}_{2}$-based samples CeO${}_{1\ensuremath{-}x}$F${}_{x}$BiS${}_{2}$ with a systematic substitution of O with F ($0<x<0.6$). In contrast to the band-structure calculations, it is found that the parent phase of CeOBiS${}_{2}$ is a bad metal instead of a band insulator. By doping electrons into the system, it is surprising to find that superconductivity appears together with a semiconducting normal state. This evolution is clearly different from the cuprate and the iron pnictide systems, and is interpreted as approaching the Pomeranchuk transition with a von Hove singularity and the possible charge-density-wave instability. Furthermore, ferromagnetism, which may arise from the Ce magnetic moments, has been observed in the low-temperature region in all samples, suggesting the coexistence of superconductivity and ferromagnetism in the superconducting samples.