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Phase Diagram of Pressure-Induced Superconductivity in EuFe2As2 Probed by High-Pressure Resistivity up to 3.2 GPa

Abstract

We have constructed a pressureβˆ’-temperature (Pβˆ’TP-T) phase diagram of PP-induced superconductivity in EuFe2_2As2_2 single crystals, via resistivity (ρ\rho) measurements up to 3.2 GPa. As hydrostatic pressure is applied, an antiferromagnetic (AF) transition attributed to the FeAs layers at T0T_\mathrm{0} shifts to lower temperatures, and the corresponding resistive anomaly becomes undetectable for PP β‰₯\ge 2.5 GPa. This suggests that the critical pressure PcP_\mathrm{c} where T0T_\mathrm{0} becomes zero is about 2.5 GPa. We have found that the AF order of the Eu2+^{2+} moments survives up to 3.2 GPa without significant changes in the AF ordering temperature TNT_\mathrm{N}. The superconducting (SC) ground state with a sharp transition to zero resistivity at TcT_\mathrm{c} ∼\sim 30 K, indicative of bulk superconductivity, emerges in a pressure range from PcP_\mathrm{c} ∼\sim 2.5 GPa to ∼\sim 3.0 GPa. At pressures close to but outside the SC phase, the ρ(T)\rho(T) curve shows a partial SC transition (i.e., zero resistivity is not attained) followed by a reentrant-like hump at approximately TNT_\mathrm{N} with decreasing temperature. When nonhydrostatic pressure with a uniaxial-like strain component is applied using a solid pressure medium, the partial superconductivity is continuously observed in a wide pressure range from 1.1 GPa to 3.2 GPa.Comment: 7 pages, 6 figures, accepted for publication in Physical Review B, selected as "Editors' Suggestion

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