  The iron pnictides and the cuprates represent two families of materials,
where strong antiferromagnetic correlation drives three other distinct ordering
tendencies: (1) superconducting pairing, (2) Fermi surface distortion, and (3)
orbital current order. We propose that (1)-(3) and the antiferromagnetic
correlation are the hallmarks of a class of strongly correlated materials to
which the cuprates and pnictides belong. In this paper we present the results
of the functional renormalization group studies to support the above claim. In
addition, we show that as a function of the interlayer hopping parameter, the
double layer Hubbard model nicely interpolates between the cuprate and the iron
pnictide physics. Finally, as a check, we will present the renormalization
group study of a ladder version of the iron pnictide, and compare the results
to those of the two-dimensional model.
