Mott localization in a pure stripe antiferromagnet Rb${}_{1-\delta }$Fe${}_{1.5-\sigma }$S${}_2$

Abstract

A combination of neutron diffraction and angle-resolved photoemission spectroscopy measurements on a pure antiferromagnetic stripe Rb${}_{1-\delta }$Fe${}_{1.5-\sigma }$S${}_2$ is reported. A neutron diffraction experiment on a powder sample shows that a 98$\%$ volume fraction of the sample is in the antiferromagnetic stripe phase with rhombic iron vacancy order and a refined composition of Rb${}_{0.66}$Fe${}_{1.36}$S${}_2$, and that only 2$\%$ of the sample is in the block antiferromagnetic phase with $\sqrt{5}\times \sqrt{5}$ iron vacancy order. Furthermore, a neutron diffraction experiment on a single crystal shows that there is only a single phase with the stripe antiferromagnetic order with the refined composition of Rb${}_{0.78}$Fe${}_{1.35}$S${}_2$, while the phase with block antiferromagnetic order is absent. Angle-resolved photoemission spectroscopy measurements on the same crystal with the pure stripe phase reveal that the electronic structure is gapped at the Fermi level with a gap larger than 0.325 eV. The data collectively demonstrates that the extra 10$\%$ iron vacancies in addition to the rhombic iron vacancy order effectively impede the formation of the block antiferromagnetic phase; the data also suggest that the stripe antiferromagnetic phase with rhombic iron vacancy order is a Mott insulator.

5 pages, 4 figures, to be published on PRB Rapid Communications

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• Spin waves and magnetic exchange interactions in the spin ladder compound RbFe${}_2$Se${}_3$
• Intertwined magnetic and nematic orders in semiconducting KFe${}_{0.8}$Ag${}_{1.2}$Te${}_2$
• Flatband-Induced Itinerant Ferromagnetism in RbCo${}_2$Se${}_2$
• Elucidating the magnetic and superconducting phases in the alkali metal intercalated iron chalcogenides
• Anisotropic magnetic excitations of a frustrated bilinear-biquadratic spin model -- Implications for spin waves of detwinned iron pnictides
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• Observation of a C-type short range antiferromagnetic order in expanded FeS
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