C-axis transport of pnictide superconductors

Müller P, Koval Y, Lazareva I, Steiner C, Wurmehl S, Büchner B, Stürzer T, Johrendt D (2017)

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2017


Publisher: Wiley-VCH Verlag

Book Volume: 254

Article Number: 1600157

Journal Issue: 1

DOI: 10.1002/pssb.201600157


The generic structure of most high T superconductors is a stacking sequence of superconducting planes separated by so-called charge reservoir layers. It is well known that carrier doping of these materials is achieved either by substitution of atoms or by nonstoichiometry in the charge reservoir layer. The alternating type of stacking causes yet another two important consequences. First, the transport anisotropy of these materials can be so high, that in the superconducting state the c-axis transport is governed by the intrinsic Josephson effect. Whereas the anisotropy of our investigated LaOFFeAs samples was not sufficient, optimum-doped Ca(FeAs)PtAs showed hysteretic c-axis current–voltage characteristics. Together with the Ambegaokar–Baratoff like temperature dependence of the critical current, this is a strong indication of intrinsic Josephson effects. Second, it is possible to deposit in the charge reservoir layers a substantial amount of charge only by injecting large c-axis currents. By charge compensation, this decreases the concentration of mobile electrons in the conducting layers of electron-doped materials. We were able to verify this in all details by c-axis transport measurements of LaOFFeAs single crystals and pure and Pt doped (CaFePtAs)PtAs single crystals. After current injection, we observed a decrease of T for doping levels at or below the T maximum, and a T increase for doping levels beyond the maximum. In all cases, the resistivity of the samples increased significantly. In both material classes, heavily overdoped samples showed a spectacular T increase by more than 10 K only accomplished by carrier injection. Generic stacking sequence of layered superconductors and crystal structure of the pnictide LaOFeAs.

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Müller, P., Koval, Y., Lazareva, I., Steiner, C., Wurmehl, S., Büchner, B.,... Johrendt, D. (2017). C-axis transport of pnictide superconductors. physica status solidi (b), 254(1). https://doi.org/10.1002/pssb.201600157


Müller, Paul, et al. "C-axis transport of pnictide superconductors." physica status solidi (b) 254.1 (2017).

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