Iron Superconductors: A Brief Introduction to Effective Low-Energy Models and Some RPA Results

When: Wednesday, April 03, 2013 at 4:00 pm
Where: DA 114
Speaker: Professor Martins
Organization: Oakland University, Michigan
Sponsor: Condensed Matter Physics

The parent compound of the iron pnictides/chalcogenides , in most of the known families, 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.

Host: Assistant Professor Adrian Feiguin