Contrasting electronic states of RuI3 and RuCl3

Abstract

The spin-orbital entangled states are of great interest as they hold exotic phases and intriguing properties. Here we use first-principles calculations to investigate the electronic and magnetic properties of RuI${}_3$ and RuCl${}_3$ in both bulk and monolayer cases. Our results show that RuI${}_3$ bulk is a paramagnetic metal, which is in agreement with recent experiments. We find that the Ru${}^{3+}$ ion of RuI${}_3$ is in the spin-orbital entangled $j_{\mathrm{eff}}=\frac{1}{2}$ state. More interestingly, a metal-insulator transition occurs from RuI${}_3$ bulk to monolayer, and this is mainly due to the band narrowing with the decreasing lattice dimensionality and to the Ru-I hybridization altered by the I $5p$ spin-orbit coupling. In contrast, RuCl${}_3$ bulk and monolayer both show Mott-insulating behavior, the Ru${}^{3+}$ ion is in the formal $S=\frac{1}{2}$ and $L=1$ state with a large in-plane orbital moment, and this result well explains the experimental large effective magnetic moment of RuCl${}_3$ and the strong in-plane magnetization. The present work demonstrates the contrasting spin-orbital states and the varying properties of RuI${}_3$ and RuCl${}_3$.

12 pages, 12 figures

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Cited by in corpus (6)

• Quantum spin Hall effect protected by spin U(1) quasisymmetry
• Orbital doublet driven even-spin Chern insulators
• $J=1/2$ Pseudospins and $d$-$p$ Hybridization in the Kitaev Spin Liquid Candidates Ru$X_3$ ($X$ = Cl, Br, I)
• Insulator-to-metal Mott transition facilitated by lattice deformation in monolayer $\alpha$-RuCl${}_3$ on graphite
• First-principles study of bulk stacking, $J_{\mathrm{eff}}$ picture, magnetic Hamiltonian, $g$ factors, and structural distortions of $\alpha$-RuCl${}_3$
• Low-temperature spin dynamics and absence of magnetic order in layered $\alpha$-RuI${}_3$