Spin-orbit excitation energies, anisotropic exchange, and magnetic phases of honeycomb RuCl3

TL;DR

This study uses quantum chemistry and exact-diagonalization to analyze RuCl3, revealing its electronic structure, magnetic interactions, and the potential to induce a spin-liquid state with an external magnetic field.

Contribution

It provides new insights into the electronic and magnetic properties of RuCl3, including the strength and nature of Kitaev exchange and the possibility of a magnetic-field-induced spin-liquid phase.

Findings

Kitaev exchange K is weaker than in Ir oxides but still dominant.

Electronic structure indicates a ferromagnetic K.

External magnetic field can induce a transition to a spin-liquid state.

Abstract

Using quantum chemistry calculations we shed fresh light on the electronic structure and magnetic properties of RuCl3, a proposed realization of the honeycomb Kitaev spin model. It is found that the nearest-neighbor Kitaev exchange K is weaker than in 5d5 Ir oxides but still larger than other effective spin couplings. The electronic-structure computations also indicate a ferromagnetic K in the halide, which is supported by a detailed analysis of the field-dependent magnetization. From exact-diagonalization calculations for extended Kitaev-Heisenberg Hamiltonians we additionally find that a transition from zigzag order to a spin-liquid ground state can be induced in RuCl3 with external magnetic field.