Theoretical study of the crystal and electronic properties of α -RuI3
Abstract
The material α -RuCl3 , with a two-dimensional Ru honeycomb sublattice, has attracted considerable attention because it may be a realization of the Kitaev quantum spin liquid. Recently, a new honeycomb material, α -RuI3 , was prepared under moderately high pressure, and it is stable under ambient conditions. However, different from α -RuCl3 , α -RuI3 was reported to be a paramagnetic metal without long-range magnetic order down to 0.35 K. Here, the structural and electronic properties of the quasi-two-dimensional α -RuI3 are theoretically studied. First, based on first-principles density functional theory calculations, the ABC stacking honeycomb-layer R 3 ¯ (No. 148) structure is found to be the most likely stacking order for α -RuI3 along the c axis. Furthermore, both R 3 ¯ and P 3 ¯1 c are dynamically stable because no imaginary frequency modes were obtained in the phononic dispersion spectrum without Hubbard U . Moreover, the different physical behavior of α -RuI3 compared to α -RuCl3 can be understood naturally. The strong hybridization between Ru 4 d and I 5 p orbitals decreases the "effective" atomic Hubbard repulsion, leading the electrons of RuI3 to be less localized than in RuCl3. As a consequence, the effective electronic correlation is reduced from Cl to I, leading to the metallic nature of α -RuI3 . Based on the DFT +U (Ueff=2 eV) plus spin-orbital coupling, we obtained a spin-orbit Mott insulating behavior for α -RuCl3 and, with the same procedure, a metallic behavior for α -RuI3 , in good agreement with experimental results. Furthermore, when introducing large (unrealistic) Ueff=6 eV, the spin-orbit Mott gap opens in α -RuI3 as well, supporting the physical picture we are proposing. Our results provide guidance to experimentalists and theorists working on two-dimensional transition metal tri-iodide layered materials.
- Publication:
-
Physical Review B
- Pub Date:
- February 2022
- DOI:
- 10.1103/PhysRevB.105.085107
- arXiv:
- arXiv:2111.04560
- Bibcode:
- 2022PhRvB.105h5107Z
- Keywords:
-
- Condensed Matter - Strongly Correlated Electrons
- E-Print:
- 9 pages, 8 figures