2013/08/06 by P. Pecchio, D. Daghero, G. A. Ummarino +5 · 18 citations
Materials Science · Physics and Astronomy · #Condensed matter physics #Coupling (piping) #Doping #Energy (signal processing) #Iron-based superconductors research #Materials science #Phase (matter) #Phase diagram #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Rare-earth and actinide compounds #Superconductivity #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.88.174506
published in Physical Review B 88(17) (American Physical Society) · 8 pages, 5 color figures
arxiv created 2013/08/06 · openalex publication_date 2013/11/11 · arxiv updated 2013/12/10 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The dependence of the superconducting gaps in epitaxial Ba(Fe_1\ensuremath-xCox)2As2 thin films on the nominal doping x (0.04\ensuremath\leqslantx\ensuremath\leqslant0.15) was studied by means of point-contact Andreev-reflection spectroscopy. The normalized conductance curves were well fitted by using the two-dimensional Blonder-Tinkham-Klapwijk model with two nodeless, isotropic gaps---although the possible presence of gap anisotropies cannot be completely excluded. The amplitudes of the two gaps \ensuremathΔS and \ensuremathΔL show similar monotonic trends as a function of the local critical temperature TcA (measured in the same point contacts) from 25 K down to 8 K. The dependence of the gaps on x is well correlated to the trend of the critical temperature, i.e., to the shape of the superconducting region in the phase diagram. When analyzed within a simple three-band Eliashberg model, this trend turns out to be compatible with a mechanism of superconducting coupling mediated by spin fluctuations, whose characteristic energy scales with Tc according to the empirical law \ensuremathΩ0=4.65kBTc, and with a total electron-boson coupling strength \ensuremathλtot=2.22 for x\ensuremath\leqslant0.10 (i.e., up to optimal doping) that slightly decreases to \ensuremathλtot=1.82 in the overdoped samples (x=0.15).