  Recent high-pressure studies found that superconductivity can be achieved
under very low pressure in the parent iron arsenide compound CaFe2As2, although
details of the sharpness and temperature of transitions vary between liquid
medium and gas medium measurements. To better understand this issue, we
performed high-pressure susceptibility and transport studies on CaFe2As2, using
helium as the pressure medium. The signatures of the transitions to the
low-temperature orthorhombic and collapsed tetragonal phase remained
exceptionally sharp and no signature of bulk superconductivity was found under
our hydrostatic conditions. Our results suggest that phase separation and
superconductivity in CaFe2As2 are induced by non-hydrostatic conditions
associated with the frozen liquid media.
