Superconducting gap structure and symmetry in hole doped BaFe2As2

BaFe2As2 is one of the heavily investigated compounds in the
Fe-pnictide family. Hole doping is achieved by doping in K on Ba
sites.  The parent compound is known to be an antiferromagnetic(AFM)
metal with a Spin Density Wave order. As one dopes the system the AFM
gives way to the coexistence region where AFM and
superconductivity(SC) coexist. Doping further leads to exclusively SC
behavior which remains all the way up to 100% K-doping. The character
of the SC varies from one end to other and there are several
interesting features across the phase diagram.  In this talk I shall
present our approach towards understanding the physics behind the hole
doped pnictides. I shall present how a simple technique can be used to
understand this doping dependence in terms of fermi-surface topology
and also show how dramatic changes can occur in the coexistence region
which involves reconstruction of the electron and hole pockets.