Electronic and spin dynamics in the insulating iron pnictide NaFe${}_{0.5}$Cu${}_{0.5}$As

Abstract

NaFe${}_{0.5}$Cu${}_{0.5}$As 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 Fe${}^{3+}$spin degree of freedom is quantified as a quasi-1D $S=\frac{5}{2}$ Heisenberg model. The itinerant As hole state is downfolded to a $p_{xy}$-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.

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• NaFe${}_{0.56}$Cu${}_{0.44}$As: A pnictide insulating phase induced by on-site Coulomb interaction
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Cited by in corpus (3)

• Spin dynamics in NaFeAs and NaFe${}_{0.53}$Cu${}_{0.47}$As probed by resonant inelastic X-ray scattering
• RKKY coupled local moment magnetism in NaFe${}_{1-x}$Cu${}_x$As
• Quasi-one-dimensional spin excitations in the iron pnictide NaFe${}_{0.53}$Cu${}_{0.47}$As