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Title: Superconducting gap evolution in overdoped BaFe₂(As1-xPx)₂ single crystals through nanocalorimetry

We report on specific heat measurements on clean overdoped BaFe₂(As1-xPx)₂ single crystals performed with a high resolution membrane-based nanocalorimeter. A nonzero residual electronic specific heat coefficient at zero temperature γr=C/T|T→0 is seen for all doping compositions, indicating a considerable fraction of the Fermi surface ungapped or having very deep minima. The remaining superconducting electronic specific heat is analyzed through a two-band s-wave α model in order to investigate the gap structure. Close to optimal doping we detect a single zero-temperature gap of Δ₀~5.3 me V, corresponding to Δ₀/kBTc ~ 2.2. Increasing the phosphorus concentration x, the main gap reduces till a value of Δ₀ ~ 1.9 meV for x = 0.55 and a second weaker gap becomes evident. From the magnetic field effect on γr, all samples however show similar behavior [γr(H) - γr (H = 0)∝ Hn, with n between 0.6 and 0.7]. This indicates that, despite a considerable redistribution of the gap weights, the total degree of gap anisotropy does not change drastically with doping.
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Publication Date:
OSTI Identifier:
Publisher's Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 91; Journal Issue: 24; Journal ID: ISSN 1098-0121
American Physical Society
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States