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arXiv · 2412.00220

Origin of the insulating state in the Kitaev candidate Cu$_2$IrO$_3$

Ying Li·Roger D. Johnson·Yogesh Singh·Radu Coldea·Roser Valentí
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Abstract

Through a combination of crystal symmetry analysis and density functional theory calculations we unveil a possible microscopic origin of the unexpected insulating behavior reported in the honeycomb Kitaev material Cu$_2$IrO$_3$. Our study suggests that this material hosts an instability towards charge ordering of the Ir ions, with alternating magnetic Ir$^{4+}$ and non-magnetic Ir$^{3+}$ ions arranged on the honeycomb lattice. In this case, the next-nearest-neighbor interactions that couple magnetic Ir$^{4+}$ ions form an enlarged triangular lattice, instead of the expected honeycomb lattice. The magnetic Cu$^{2+}$ ions located at the centre of the iridium honeycomb voids also form a triangular lattice, and additionally contribute to the magnetization of the system. Together, the interpenetrated Ir$^{4+}$ and Cu$^{2+}$ triangular lattices present a novel type of honeycomb Kitaev lattice composed of two types of magnetic ions.

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Ying Li, Roger D. Johnson, Yogesh Singh, Radu Coldea, Roser Valentí. 2024-11-29. Origin of the insulating state in the Kitaev candidate Cu$_2$IrO$_3$. https://arxiv.org/abs/2412.00220

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