Evidence from neutron diffraction for superconductivity in the stabilized tetragonal phase of CaFe_2As_2 under uniaxial pressure

摘要

CaFe_2As_2 single crystals under uniaxial pressure applied along the c axis exhibit the coexistence of several structural phases at low temperatures. We show that the room-temperature tetragonal phase is stabilized at low temperatures for pressures above 0.06 GPa, and its weight fraction attains a maximum in the region where superconductivity is observed under applied uniaxial pressure. Simultaneous resistivity measurements strongly suggest that this phase is responsible for the superconductivity in CaFe_2As_2 found below 10 K in samples subjected to nonhydrostatic pressure conditions.