3 research outputs found
Disorder induced transition between s_+- and s_++ states in two-band superconductors
We have reexamined the problem of disorder in two-band superconductors, and
shown within the framework of the T-matrix approximation, that the suppression
of T_c can be described by a single parameter depending on the intraband and
interband impurity scattering rates. T_c is shown to be more robust against
nonmagnetic impurities than would be predicted in the trivial extension of
Abrikosov-Gor'kov theory. We find a disorder-induced transition from the
s_{\pm} state to a gapless and then to a fully gapped s_{++} state, controlled
by a single parameter -- the sign of the average coupling constant .
We argue that this transition has strong implications for experiments.Comment: 5 pages, 4 figures; suppl. material: 3 pages, 2 figures; published
versio
Gap symmetry and structure of Fe-based superconductors
The recently discovered Fe-pnictide and chalcogenide superconductors display
low-temperature properties suggesting superconducting gap structures which
appear to vary substantially from family to family, and even within families as
a function of doping or pressure. We propose that this apparent nonuniversality
can actually be understood by considering the predictions of spin fluctuation
theory and accounting for the peculiar electronic structure of these systems,
coupled with the likely 'sign-changing s-wave' (s\pm) symmetry. We review
theoretical aspects, materials properties and experimental evidence relevant to
this suggestion, and discuss which further measurements would be useful to
settle these issues.Comment: 86 pages, revie