Electronic phase diagram in a new BiS2-based Sr1−xLaxFBiS2 system

Abstract

In this paper, we systematically study the effect of electron doping in a new BiS2-based system Sr1−xLaxFBiS2 (0 ≤x ≤ 0.7) through the multiple techniques of x-ray diffraction, electrical transport, magnetic susceptibility, and Hall effect measurements. The parent compound SrFBiS2 is found to possess a semiconductor-like ground state, with a thermal activation energy Eg ∼ 38 meV. By the partial substitution of La for Sr, superconductivity emerges when x > 0.3, reaching its maximal superconducting transition temperature of Tc ∼ 3.5 K at x = 0.55. In the normal state of superconducting samples, it is clearly seen that there exists a crossover from the metallic to the semiconducting state below a temperature Tmin, which shifts to lower temperatures with increasing La content. Based on these measurements, the associated electronic phase diagram of the Sr1−xLaxFBiS2 system has thus been established.