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Superconductivity at 44 K in K intercalated FeSe system with excess Fe.

ABSTRACT: We report here that a new superconducting phase with much higher Tc has been found in K intercalated FeSe compound with excess Fe. We successfully grew crystals by precisely controlling the starting amount of Fe. Besides the superconducting (SC) transition at ~30 K, we observed a sharp drop in resistivity and a kink in susceptibility at 44 K. By combining thermodynamic measurements with electron spin resonance (ESR), we demonstrate that this is a new SC transition. Structural analysis unambiguously reveals two phases coexisting in the crystals, which are responsible respectively for the SC transitions at 30 and 44 K. The structural experiments and first-principles calculations consistently indicate that the 44 K SC phase is close to a 122 structure, but with an unexpectedly large c-axis of 18.10 Å. We further find a novel monotonic dependence of the maximum Tc on the separation of neighbouring FeSe layers.

SUBMITTER: Zhang AM

PROVIDER: S-EPMC3564023 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Superconductivity at 44 K in K intercalated FeSe system with excess Fe.

Zhang An-min AM Xia Tian-long TL Liu Kai K Tong Wei W Yang Zhao-rong ZR Zhang Qing-ming QM

Scientific reports 20130205

We report here that a new superconducting phase with much higher Tc has been found in K intercalated FeSe compound with excess Fe. We successfully grew crystals by precisely controlling the starting amount of Fe. Besides the superconducting (SC) transition at ~30 K, we observed a sharp drop in resistivity and a kink in susceptibility at 44 K. By combining thermodynamic measurements with electron spin resonance (ESR), we demonstrate that this is a new SC transition. Structural analysis unambiguou ...[more]

PMID: 23386972

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