Hydrostatic Pressure Studies on Parent Phase SrFBiS2 of BiS2-Based Superconducting Family

Recently discovered BiS 2 -based layered superconductors have gained tremendous interest in the scienti fi c community. These BiS 2 -based superconductors have superconducting transition temperature ( T c ) as 4.5 K for Bi 4 O 4 S 3 , 1 , 2 ) 2 – 5K for REO / FBiS 2 (La, Ce, Pr, Nd) 3 – 6 ) and 2.8 K for Sr 0.5 La 0.5 - FBiS 2 . 7 ) It is interesting to note that their parent phases LaOBiS 2 3 ) and SrFBiS 2 8 ) are semiconducting, which upon the O / F doping in former 3 – 6 ) and Sr / RE doping in later 7 ) become superconducting. Superconducting transition temper- ature in REO 0.5 F 0.5 BiS 2 RE (La, Ce, Pr, Nd) is observed to increase under the hydrostatic pressure by three fold just in 2 GPa pressure. 9 – 14 ) It is suggested that this dramatic increase in T c is related to a structural phase transition under pressure especially for LaO 0.5 F 0.5 BiS 2 as reported by Tomita et al. 13 ) Recently, we found that the T c of Sr 0.5 La 0.5 FBiS 2 super- conductor increased by fi vefold from around 2 K to above 10 K, accompanied by the semiconducting to metallic normal state. 15 ) Keeping in view, that application of hydrostatic pressure has resulted in tremendous increase of T c for the BiS 2 based superconductors, 9 – 15 ) one wonders how their non- superconducting parent compounds will respond to the same. In the present work, we measure the temperature dependent electrical resistivity from 300 K down to 2 K under applied hydrostatic pressure (0 – 2.5 GPa) for SrFBiS 2 , which is the parent compound for the BiS 2 -based superconductors. 8