Mott transition in Modulated Lattices and Parent Insulator of   (K,Tl)yFexSe2 Superconductors
  The degree of electron correlations remains a central issue in the iron-based superconductors. The parent iron pnictides are antiferromagnetic, and their bad-metal behavior has been interpreted in terms of proximity to a Mott transition. We study such a transition in multi-orbital models on modulated lattices containing an ordered pattern of iron vacancies, using a slave-rotor method. We show that the ordered vacancies lead to a band-narrowing, which pushes the system to the Mott insulator side. This effect is proposed to underlie the insulating behavior observed in the parent compounds of the newly discovered (K,Tl)yFexSe2 superconductors. 
Rong Yu, Jian-Xin Zhu, Qimiao Si
cond-mat.supr-con cond-mat.str-el