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We have investigated the specific heat of optimally doped iron chalcogenide superconductor Fe(Te0.57Se0.43) with a high-quality single crystal sample. The electronic specific heat Ce of this sample has been successfully separated from the phonon contribution using the specific heat of a nonsuperconducting sample (Fe0.90Cu0.10)(Te0.57Se0.43) as a reference. The normal-state Sommerfeld coefficient γn of the superconducting sample is found to be ~26.6 mJ/mol K2, indicating intermediate electronic correlation. The temperature dependence of Ce in the superconducting state can be best fitted using a double-gap model with 2Δs(0)/kBTc=3.92 and 2Δl(0)/kBTc=5.84. The large gap magnitudes derived from fitting, as well as the large specific heat jump of ΔCe(Tc)/γnTc~2.11, indicate strong-coupling superconductivity. Furthermore, the magnetic field dependence of specific heat shows strong evidence for multiband superconductivity

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Physical Review B


Copyright 2011 American Physical Society

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