Abstract
We have systematically studied the low-temperature specific heat of the single crystals covering the whole superconducting dome. Using the nonsuperconducting heavily overdoped sample as a reference for the phonon contribution to the specific heat, we find that the normal-state electronic specific heats in the superconducting samples may have a nonlinear temperature dependence, which challenges previous results in the electron-doped Ba-122 iron-based superconductors. A model based on the presence of ferromagnetic spin fluctuations may explain the data between and , suggesting the important role of Fermi-surface topology in understanding the normal-state electronic states.
- Received 16 November 2015
- Revised 30 March 2016
DOI:https://doi.org/10.1103/PhysRevB.93.134520
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