NaFe0.5Cu0.5As represents a rare exception in the metallic iron pnictide family, in which a small insulating gap is opened. Based on first-principles study, we provide a comprehensive theoretical characterization of this insulating compound. The Fe3+spin degree of freedom is quantified as a quasi-1D S=25 Heisenberg model. The itinerant As hole state is downfolded to a pxy-orbital hopping model on a square lattice. A unique orbital-dependent Hund's coupling between the spin and the hole is revealed. Several important material properties are analyzed, including (a) factors affecting the small p−d charge-transfer gap; (b) role of the extra interchain Fe; and (c) the quasi-1D spin excitation in the Fe chains. The experimental manifestations of these properties are discussed.
@article{arxiv.1708.08065,
title = {Electronic and spin dynamics in the insulating iron pnictide NaFe$_{0.5}$Cu$_{0.5}$As},
author = {Shunhong Zhang and Yanjun He and Jia-Wei Mei and Feng Liu and Zheng Liu},
journal= {arXiv preprint arXiv:1708.08065},
year = {2017}
}