Abstract
The effect of pressure on the superconductivity of "111"-type Na1−xFeAs is investigated through temperature-dependent electrical-resistance measurements in a diamond anvil cell. The superconducting transition temperature (Tc) increases from 26 K to a maximum of 31 K as the pressure increases from ambient pressure to 3 GPa. Further increasing pressure suppresses Tc drastically. The behavior of pressure-tuned Tc in Na1−x FeAs is much different from that in Lix FeAs, although they have the same Cu2Sb-type structure.