Exploring nature of the superconducting T_c, spin density wave (SDW) shift and symmetry in electron vs. hole doped Iron Pnictides (1111) under Hydrostatic Pressure.

Pressure plays a vital role in discovering & unraveling physics of novel superconductors (SC). In both High T_c cuprates & Fe-pnictides pressure (P) is important to raise T_c significantly. Layered Fe-pnictides can be obtained by electron & hole doping (x). To determine if symmetry between electron & hole doping exists, we explored sensitivity of iron pnictide SC to hydrostatic pressure & pressure induced shift in T_c & SDW by carrying out resistivity measurements under hydrostatic pressure on electron doped Sm(O_1-xF_x)FeAs & hole doped Pr_1-xSr_xFeAsO up to 1.8GPa using piston cylinder clamp cell device. Coexistence of SC & SDW behavior were observed & pressure effects on both are being investigated. Four probe resistance measurements show that with pressure T_c increases (+dT_c/dP) for under doped & T_c decreases (-dT_c/dP) for over doped compounds of Sm(O_1-xF_x)FeAs & Pr_1-xSr_xFeAsO, so signs of dT_c/dP & dT_c/dx are found to be same. SDW transition is pushed toward lower temperature, So P & x both have same suppression effect on SDW state. High pressure can compress crystalline structure of material & force its layers to be closer, which might increase material's T_c by improving pressure induced charge transfer between Fe₂As₂ & Sm(O/F), (Pr/Sr)O layers. Pressure effect on T_c of Sm(O_1-xF_x)FeAs & Pr_1-xSr_xFeAsO are being compared with that of cuprates. Results suggest a symmetry appear to exist between electron & hole doping Fe-pnictide & similar effects of P & x on T_c i.e. dT_c/dP & dT_c/dx have same sign for Fe-pnictide & cuprate.