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Iron-pnictides: A brief introduction, effective low- energy models and RPA results

George Martins (Oakland University, USA)

03.06.2011 at 10:15 

In this talk, a brief introduction to experimental and theoretical results for the iron pnictides

will be given, trying to compare its similarities and differences with the cuprates. The pnictides

parent compound, in all the families of superconducting pnictides known, is a semimetal with an

Spin Density Wave (SDW) ground state, which under doping, for some families, and under

pressure for others, becomes superconducting (max T_c ~ 56 K).

The model of choice has been a 5-band Hubbard model, with longer than nearest-neighbor tight

binding hoppings and some on-site correlation terms (although I will argue that efforts to work

with a 2-band model should be pursued). An RPA solution to this model will be presented for the

spin susceptibility and the pairing function. It will be argued that the extreme richness of the

Fermi surface (coming from all the hybridized d-states) results in RPA solutions which are very

dependent on the tight binding hopping terms and in a ‘fierce’ competition between different

symmetries for the pairing function. This may be one of the important differences in relation to

the cuprates.


A348 Theresienstr.37