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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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