Pressure-enhanced superconducting transition in the inter-block-layer electron-transfer superconductor BaTh2Fe4As4(N0.7O0.3)2

Abstract

The 12442-type hybrid structure compound BaTh2Fe4As4(N0.7O0.3)2 is a recently synthesized inter-block-layer electron-transfer superconductor with separated double Fe2As2 layer and shows the superconducting transition at Tconset∼30 K and Tczero∼20 K. Here, we perform the resistivity measurements under various hydrostatic pressures up to ∼12 GPa to track the evolution of its superconducting Tc and normal-state properties as a function of pressure. We found that Tc(P) exhibits a nonmonotonic variation with pressure forming a dome-shaped superconducting phase, i.e., Tconset first increases quickly from ∼30 K at ambient pressure to the optimal values of ∼46 K at 2.6 GPa and then decreases gradually to ∼23 K upon further increasing pressure to ∼12 GPa. However, Tczero merely increases from ∼21 K at ambient pressure to ∼24 K at 2.6 GPa and then to ∼12 K at ∼12 GPa, leading to an obvious broadening of the superconducting transition at 2.6 GPa. Concomitant with the domed-shaped superconducting phase, the linear-temperature resistivity coefficient A1 described by the empirical formula ρ=ρ0+A1T+A2T2 also exhibits a similar dome-shaped structure, which may establish the positive correlation between Tc and A1 as found in the unconventional high-Tc superconductors. Our high-pressure x-ray diffraction measurements rule out the occurrence of structural transition or a half-collapsed phase transition in the measured pressure range. Thus, our results indicate that the application of pressure may optimize the superconducting Tc by enhancing the inter-block-layer electron-transfer and/or the spin fluctuations in BaTh2Fe4As4(N0.7O0.3)2.

Source-reported materials — not catalogue approval

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