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Publications in Scientific Journals:

S.-L. Drechsler, S. Johnston, V. Grinenko, J. Tomczak, H. Rosner:
"Constraints on the total coupling strength to bosons in the iron based superconductors";
Physica Status Solidi B - Basic Solid State Physics, 254 (2017), 10; 1700006.



English abstract:
Despite the fact that the Fe-based superconductors (FeSCs)
were discovered nearly 10 years ago, the community is still
devoting a tremendous effort toward elucidating their relevant
microscopic pairing mechanism(s) and interactions. At present,
there is still no consistent interpretation of their normal state
properties, where the strength of the electron-electron interaction
and the role of correlation effects are under debate. Here,
we examine several common materials and illustrate various
problems and concepts that are generic for all FeSCs. Based
on empirical observations and qualitative insight from density
functional theory, we show that the superconducting and
low-energy thermodynamic properties of the FeSCs can be described
semi-quantitively within multiband Eliashberg theory.
We account for the important high-energy mass renormalizations
phenomenologically, and in agreement with constraints
provided by thermodynamic, optical, and angle-resolved photoemission
data. When seen in this way, many representative
FeSCs with Tc < 40 K studied so far are found to belong to an
intermediate coupling regime (with the possible exception of
some systems near a quantum critical point or in the vicinity of
a Lifshitz transition). This finding is in contrast to the generally
strong coupling scenarios proposed in the early period of
the FeSC history.We also discuss several related issues, including
the role of band shifts as measured by the positions of van
Hove singularities, and the nature of a recently suggested quantum
critical point in the strongly hole-doped systems AFe2As2
(A = K, Rb, Cs). Using high-precision full relativistic GGAband
structure calculations, we arrive at a somewhat milder
mass renormalization in comparison with previous studies.
From the calculated mass anisotropies of all Fermi surface
sheets, only the ε-pocket near the corner of the BZ is compatible
with the experimentally observed anisotropy of the upper critical
field, pointing to its dominant role in the superconductivity
of these three compounds.

Keywords:
Eliashberg-theory, iron-based superconductors, superconductivity


"Official" electronic version of the publication (accessed through its Digital Object Identifier - DOI)
http://dx.doi.org/10.1002/pssb.201700006


Created from the Publication Database of the Vienna University of Technology.