Iron pnictides: unconventional s-wave superconductors

Synopsis

Superconductivity results from condensation of bound electron pairs, the so-called Cooper pairs. In the conventional Bardeen-Cooper-Schrieffer theory, the attraction between electrons originates from their interaction with the ionic lattice and the exchange of quanta of the lattice vibrations, phonons. The resulting wavefunction for the Cooper pairs carries zero angular momentum, leading to s-wave superconductivity. 

In the usual classification, unconventional superconductors are those with non s-wave Cooper pairing.

In this talk, a review of phenomenology of iron based superconductors will be presented. An argument will be made for a novel unconventional mechanism of s-wave Cooper pairing in the iron pnictides with large concentration of holes. This mechanism is favored by the spin-orbit interaction and Hund interaction, and is capable of explaining some of their non-trivial experimental features.