Sn substitution effect on the superconductivity of layered oxychalcogenide La2O2Bi3Ag1-xSnxS6.

Recently, we reported the superconductivity in layered oxychalcogenide La2O2Bi3AgS6. In this study, we have investigated the substitution effect of Sn for the Ag site in La2O2Bi3Ag1-xSnxS6. The superconducting transition temperature (Tc) increased with increasing Sn concentration up to x = 0.4 and reached a maximum Tc of 2.4 K for x = 0.4. As well, we observed a hump in the normal state resistivity at the anomaly temperature (T*) nearly 180 K for x = 0. The T* decreased with increasing Sn concentration and disappeared at x = 0.3. From the analogy to EuFBiS2, which undergoes a superconducting transition at temperatures below a charge-density-wave (CDW) transition, the La2O2Bi3Ag1-xSnxS6 system would be a good candidate to study the relationship between superconductivity and CDW states. The upper critical field (Bc2) for x = 0.4 was analyzed by a model Bc2(T)=Bc2*(1-T/Tc)1+{alpha} to estimate Bc2(0). The Bc2 estimated from the onset of the resistive transition was 3.33 T for x = 0.4.