Spectroscopic signature of trimer Mott insulator and charge disproportionation in BaIrO${}_3$

Abstract

We have measured the reflectivity spectra of the barium iridate $9R$ BaIrO${}_3$, the crystal structure of which consists of characteristic Ir${}_3$O${}_{12}$ trimers. In the high-temperature phase above the transition temperature $T_c\simeq 180$ K, we find that the optical conductivity involves two temperature-dependent optical transitions with an ill-defined Drude response. These features are reminiscent of the optical spectra in the organic dimer Mott insulators, implying a possible emergence of an unusual electronic state named trimer Mott insulator in BaIrO${}_3$, where the carrier is localized on the trimer owing to the strong Coulomb repulsion. Along with a pronounced splitting of the phonon peak observed below $T_c$, which is a hallmark of charge disproportionation, we discuss a possible phase transition from the trimer Mott insulator to a charge-ordered insulating phase in BaIrO${}_3$.

arXiv comment6 pages, 4 figures, to be published in Phys. Rev. B

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Cited by in corpus (3)

• Emergence of spinons in layered trimer iridate Ba4Ir3O10
• Structural and Magnetic Transitions in the Planar Antiferromagnet Ba${}_4$Ir${}_3$O${}_{10}$
• Quasimolecular electronic structure of the trimer iridate Ba${}_4$NbIr${}_3$O${}_{12}$