Electronic and spin dynamics in the insulating iron pnictide NaFe0.5Cu0.5As

Shunhong Zhang; Yanjun He; Jia-Wei Mei; Feng Liu; Zheng Liu

doi:10.1103/PhysRevB.96.245128

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Electronic and spin dynamics in the insulating iron pnictide NaFe0.5Cu0.5As

Shunhong Zhang, Yanjun He, Jia-Wei Mei, Feng Liu, Zheng Liu

DOI 10.1103/PhysRevB.96.245128 · Physical Review B

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Abstract

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-one-dimensional (1D) S=52 Heisenberg model. The itinerant As hole state is downfolded to a pxy-orbital hopping model on a square lattice. An orbital-dependent Hund's coupling between the spin and the hole is revealed. Several important material properties are analyzed, including (a) the factors affecting the small p−d charge-transfer gap; (b) the role of extra interchain Fe atoms; and (c) quasi-1D spin excitation in the Fe chains. The experimental manifestations of these properties are discussed.