Suppression of antiferromagnetic order by strain-enhanced frustration in honeycomb cobaltate.

Layered honeycomb cobaltates are predicted as promising for realizing the Kitaev quantum spin liquid, a many-body quantum entangled ground state characterized by fractional excitations. However, they exhibit antiferromagnetic ordering at low temperatures, hindering the expected quantum state. We demonstrate that controlling the trigonal distortion of CoO octahedra is crucial to suppress antiferromagnetic order through enhancing frustration in layered honeycomb cobaltates.