Effect of pressure on a 111-type iron pnictide superconductor

The behavior of superconductivity of o111o-type iron pnictide superconductors, namely, LiFeAs, NaFeAs and LiFeP, is investigated at different pressures through electrical resistance measurements. For LiFeAs and LiFeP, the superconducting transition temperature Tc decreases monotonously with increasing pressure, with the pressure coefficient of dTc/dP being-1.38 and-1.26K/GPa, respectively. The Tc of NaFeAs increases to a maximum value with the pressure increasing to 3GPa; further increasing the pressure suppresses Tc with the slope of dTc/dP about-3.40K/GPa.