paper

Crystal structure and magnetism in -RuCl3: an ab-initio study

arXiv:1509.04723 · doi:10.1103/PhysRevB.93.155143

Abstract

-RuCl has been proposed recently as an excellent playground for exploring Kitaev physics on a two-dimensional (2D) honeycomb lattice. However, structural clarification of the compound has not been completed, which is crucial in understanding the physics of this system. Here, using {\it ab-initio} electronic structure calculations, we study a full three dimensional (3D) structure of -RuCl including the effects of spin-orbit coupling (SOC) and electronic correlations. Three major results are as follows; i) SOC suppresses dimerization of Ru atoms, which exists in other Ru compounds such as isostructural LiRuO, and making the honeycomb closer to an ideal one. ii) The nearest-neighbor Kitaev exchange interaction between the =1/2 pseudospin depends strongly on the Ru-Ru distance and the Cl position, originating from the nature of the edge-sharing geometry. iii) The optimized 3D structure without electronic correlations has space group symmetry independent of SOC, but including electronic correlation changes the optimized 3D structure to either or within 0.1 meV per formula unit (f.u.) energy difference. The reported structure is also close in energy. The interlayer spin exchange coupling is a few percent of in-plane spin exchange terms, confirming -RuCl is close to a 2D system. We further suggest how to increase the Kitaev term via tensile strain, which sheds new light in realizing Kitaev spin liquid phase in this system.

10 pages, 10 figures, and 4 tables

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