Ground state in proximity to a possible Kitaev spin liquid: The undistorted honeycomb iridate Na x IrO 3 ( 0.60 ≤ x ≤ 0.80 )

The Kitaev quantum spin liquid has been among the most intensively studied states of matter but there has been no clear-cut materials realization of it. This absence is largely because all existing honeycomb lattices are inherently distorted and disordered, which inevitably amplifies the competing Heisenberg interaction in the Kitaev-Heisenberg model, leading to an unwanted antiferromagnetic state. This work reports a new, undistorted honeycomb iridate NaxIrO${}_{3}$, where all evidence indicates that the elusive Kitaev spin liquid may finally be within reach.