The vicinity of hyper-honeycomb $\beta$-Li2IrO3 to a three-dimensional Kitaev spin liquid state

TL;DR

This paper explores the hyper-honeycomb iridate $eta$-Li2IrO3, showing it is close to a three-dimensional Kitaev spin liquid state due to dominant Kitaev interactions and how slight modifications could realize this exotic quantum phase.

Contribution

The study provides a detailed theoretical analysis of the magnetic interactions in $eta$-Li2IrO3, highlighting its proximity to a 3D Kitaev spin liquid state and suggesting pathways to realize it experimentally.

Findings

Large ferromagnetic first-neighbor Kitaev interactions identified

Second-neighbor antiferromagnetic Heisenberg exchange influences ground state

System is close to a 3D Kitaev spin liquid phase, tunable by strain

Abstract

Due to the combination of a substantial spin-orbit coupling and correlation effects, iridium oxides hold a prominent place in the search for novel quantum states of matter, including, e.g., Kitaev spin liquids and topological Weyl states. We establish the promise of the very recently synthesized hyper-honeycomb iridate $\beta$-Li2IrO3 in this regard. A detailed theoretical analysis reveals the presence of large ferromagnetic first-neighbor Kitaev interactions, while a second-neighbor antiferromagnetic Heisenberg exchange drives the ground state from ferro to zigzag order via a three-dimensional Kitaev spin liquid and an incommensurate phase. Experiment puts the system in the latter regime but the Kitaev spin liquid is very close and reachable by a slight modification of the ratio between the second- and first-neighbor couplings, for instance via strain.