Theoretical Model Study of Low-Energy Spin Excitations in Iron Chalcogenide AxFe2−xSe2: One Band Approach

Abstract

In this paper, we propose a one band tight binding model Hamiltonian for the newly discovered 122-type Selenide family of the iron-based system incorporated with the nearest-neighbor (NN) and the next-nearest-neighbor (NNN) hopping integrals [Formula: see text] and [Formula: see text], respectively. The spin–spin interactions of the electrons leading to the antiferromagnetic spin density wave (SDW) order have been studied at wave vector [Formula: see text]. The electron Green’s functions are calculated from the Hamiltonian model using Green’s function technique and finally the SDW gap equation is derived and studied using their NN and NNN spin coupling [Formula: see text] and [Formula: see text], respectively.