Investigation of magnetic and transport properties of La0.8Sm0.2O0.5F0.5BiS2 superconductor under external hydrostatic pressure

Abstract

The dc electrical resistivity and magnetization measurements as a function of temperature 1.8-300 K were formed at external hydrostatic pressures on normal and superconducting state of new polycrystalline BiS2 based layered La0.2Sm0.8BiS2O00.5F0.5 superconductor. In situ, electrical resistivity measurements, At ambient pressure the superconducting transition temperature (Tc) at ~3 K which are enhanced substantially under external pressure to 10.3 K at 1.74 GPa with positive pressure coefficient, dTc/dP= 4.19 K/GPa. Further increasing pressure Tc has been decreased upto 6.2 K at 1.96 GPa with negative pressure coefficient dTc/dP= -2.09 K/GPa. From the normal state resistivity exhibits the strong suppression of the semiconducting behavior in La/SmO0.5F0.5BiS2 compounds suggests that the Fermi surface is in the vicinity of some instability. We report here the enhancement of Tc from 2.83 to 5.86 K with small increase in pressure upto 0.8 GPa with similar pressure coefficient of dTc/dP= 3.78 K/GPa. However, it should be noted that either chemical substitution or physical pressure on these systems show a dome shaped Tc variation which means that the enhancement may not be achieved for higher doping concentration and (or) pressure s beyond an optimum level. In our results, exhibits which higher Tc may be achieved lies around 1.74 GPa. Above this pressure the Tc may decrease and exhibit a dome shaped behavior similar to other rare –earth systems of BiS2 and Fe-based superconductors. Substantial enhancement of superconductivity under moderate pressure in studied new BiS2 based superconductors call for the attention of condensed matter physics community.