Fermi surface nesting and spin density wave instability in the overdoped superconducting iron pnictides

¹ Department of Physics, Hangzhou Normal University - Hangzhou, China
² Department of Physics and Center of Theoretical and Computational Physics, The University of Hong Kong Hong Kong, China

Received: 31 August 2012
Accepted: 5 November 2012

Abstract

The nesting of electron Fermi pocket with one of the two hole pockets around the Brillouin zone center has been attributed to the spin density wave (SDW) instability in the parent compound of superconducting iron pnictides. We propose here that the second hole Fermi pocket may be nested with the electron pocket in the doped case, which results in a new SDW instability. Our work is motivated by and may explain the recent scanning tunneling spectroscopy (STM) measurements on NaFe_1−xCo_xAs, which show an asymmetric gap-like feature near the Fermi level in the overdoped regime (Zhou X. et al., Phys. Rev. Lett., 109 (2012) 037002). We use a multi-band model to examine this feature within random phase approximation to include the coupling between the itinerant electron and the local spins.