Abstract

Candidate materials for the Kitaev spin liquid phase have been intensively studied recently because of their potential applications in fault-tolerant quantum computing. Although most of the studies on Kitaev spin liquid have been done in 4d- and 5d-based transition-metal compounds, recently there has been a growing research interest in Co-based quasi-two-dimensional honeycomb magnets, such as BaCo2(AsO4)2 because of formation of spin-orbit-entangled Jeff=1/2 pseudospin moments at Co2+ sites and potential realizations of Kitaev-like magnetism therein. Here, we obtain high-accuracy crystal and electronic structure of BaCo2(AsO4)2 by employing combined density-functional and dynamical mean-field theory calculations, which correctly capture the Mott-insulating nature of the target system. We show that Co2+ ions form a high-spin configuration, S=3/2, with an active Leff=1 orbital degree of freedom, in the absence of spin-orbit coupling. The size of trigonal distortion within CoO6 octahedra is found to be not strong enough to completely quench the orbital degree of freedom, so that the presence of spin-orbit coupling can give rise to the formation of spin-orbit-entangled moments and the Kitaev exchange interaction. Our finding supports recent studies on potential Kitaev magnetism in this compound and other Co-based layered honeycomb systems.