Separation of magnetism and superconductivity in rare earth-doped CaFe2As2 by pressure

Johnpierre Paglione (Center for Nanophysics and Advanced Materials & Department of Physics, University of Maryland)

Traces of a high-Tc superconducting phase with transition temperatures approaching 50 K have been stabilized by the substitution of light rare earths for Ca atoms in the iron-pnictide material CaFe2As2. I will present our recent studies of the evolution of superconductivity and magnetism in single crystals of La-doped CaFe2As2 under both quasi-hydrostatic and hydrostatic applied pressures by means of transport, magnetic, and neutron scattering measurements. Upon pressure increase, we find evidence that the "50 K" superconducting phase is an intrinsic property of the materials. However, unlike transition metal-doped 122 iron-superconductors where superconductivity happily coexists with AFM, the little coexistence of SC and AFM appears to mimic that found in 1111 iron-superconductors, suggesting a similar phase diagram. I will discuss this unusual dichotomy between lower-Tc systems that happily coexist with AFM and the tendency for the highest-Tc systems to show phase separation.

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