Superconductivity at 25K under hydrostatic pressure for FeTe0.5Se0.5   superconductor
  We report the impact of hydrostatic pressure on the superconductivity and normal state resistivity of FeTe0.5Se0.5 superconductor. At the ambient pressure the FeTe0.5Se0.5 compound shows the superconducting transition temperature Tconset at above 13K and TcR=0 at 11.5K. We measure pressure dependent resistivity from 250K to 5K, which shows that the normal state resistivity increases initially for the applied pressures of up to 0.55GPa and then the same is decreased monotonically with increasing pressure of up to 1.97GPa. On the other hand the superconducting transition temperatures (Tconset and TcR=0) increase monotonically with increasing pressure. Namely the Tconset increases from 13K to 25K and TcR=0 from 11.5K to 20K for the pressures range of 0-1.97GPa. Our results suggest that superconductivity in this class of Fe-based compounds is very sensitive to pressure as the estimated pressure coefficient dTc(onset)/dP is 5.8K/GPa. It may be suggested that FeTe0.5Se0.5 superconductor is a strong electron correlated system. The enhancement of Tc with applying pressure is mainly attributed to an increase of charge carriers at Fermi surface. 
Rajveer Jha, Rayees A. Zargar, A. K. Hafiz, H. Kishan and V.P.S. Awana
cond-mat.supr-con