High-Tc superconductivity up to 55 K under high pressure in a heavily electron doped Li0.36(NH3)yFe2Se2 single crystal

Abstract

We report a high-pressure study on the heavily electron doped Li0.36(NH3)yFe2Se2 single crystal by using a cubic anvil cell apparatus. The superconducting transition temperature Tc≈44K at ambient pressure is first suppressed to below 20 K upon increasing pressure to Pc≈2GPa, above which the pressure dependence of Tc(P) reverses and Tc increases steadily to ca. 55 K at 11 GPa. These results thus evidence a pressure-induced second high-Tc superconducting (SC-II) phase in Li0.36(NH3)yFe2Se2 with the highest Tcmax≈55K among the FeSe-based bulk materials. Hall data confirms that in the emergent SC-II phase the dominant electron-type carrier density undergoes a fourfold enhancement and tracks the same trend as Tc(P). Interestingly, we find a nearly parallel scaling behavior between Tc and the inverse Hall coefficient for the SC-II phases of both Li0.36(NH3)yFe2Se2 and (Li,Fe)OHFeSe. The present study demonstrates that high pressure offers a distinctive means to further raise the maximum Tc of heavily electron doped FeSe-based materials by increasing the effective charge-carrier concentration via a possible Fermi-surface reconstruction at Pc.

Source-reported materials — not catalogue approval

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