"Mott localization in a pure stripe antiferromagnet Rb 1 − δ Fe 1.5 − σ S2"

Meng Wang: Ming Yi, Huibo Cao, C. de la Cruz, S. K. Mo, Q. Z. Huang, E. Bourret-Courchesne, Pengcheng Dai, D. H. Lee, Z. X. Shen, and R. J. Birgeneau; Physical Review B, 09/01/2015.

Additional Authors: Ming Yi, Huibo Cao, C. de la Cruz, S. K. Mo, Q. Z. Huang, E. Bourret-Courchesne, Pengcheng Dai, D. H. Lee, Z. X. Shen, and R. J. Birgeneau

Abstract:

A combination of neutron diffraction and angle-resolved photoemission spectroscopy measurements on a pure antiferromagnetic stripe Rb1δFe1.5σS2 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 Rb0.66Fe1.36S2, and that only 2% of the sample is in the block antiferromagnetic phase with 5×5 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 Rb0.78Fe1.35S2, 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 demonstrate 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.