Predominance of the Kitaev interaction in a three-dimensional honeycomb iridate: From ab initio to spin model

¹ Department of Physics and Center for Quantum Materials, University of Toronto - 60 St. George St., Toronto, Ontario, M5S 1A7, Canada
² Canadian Institute for Advanced Research / Quantum Materials Program - Toronto, Ontario MSG 1Z8, Canada

Received: 19 August 2015
Accepted: 17 December 2015

Abstract

The recently discovered three-dimensional hyperhoneycomb iridate, β-Li₂IrO₃, has raised hopes for the realization of the dominant Kitaev interaction between spin-orbit entangled local moments due to its near-ideal lattice structure. If true, this material may lie close to the sought-after quantum spin-liquid phase in three dimensions. Utilizing ab initio electronic structure calculations, we first show that the spin-orbit entangled basis, , correctly captures the low-energy electronic structure. The effective spin model derived in the strong-coupling limit supplemented by the ab initio results is shown to be dominated by the Kitaev interaction. We demonstrated that the possible range of parameters is consistent with a non-coplanar spiral magnetic order found in a recent experiment. All of these analyses suggest that β-Li₂IrO₃ may be the closest among known materials to the Kitaev spin-liquid regime.