  The suppression of magnetic order and the detection of a half-quantized
thermal Hall effect in {\alpha}-RuCl3 under the influence of an external
magnetic field have sparked significant debate, whether these phenomena point
to spin fractionalization, as posited by the Kitaev quantum spin liquid model,
or if they arise from more conventional mechanisms in an antiferromagnetically
ordered spin state. Here, through 23Na NMR measurements on the layered oxide
Na2Co2TeO6 at two distinct magnetic fields (4.7 and 9.4 Tesla), we provide
compelling evidence that upon cooling, Kitaev fractional excitations dominate
NMR relaxation. This remains true even at 4.7 Tesla, where NMR experiments
reveal the onset of an antiferromagnetic phase at TN ~ 25 K. Notably, below 10
K, the NMR relaxation times bifurcate into two components: one retaining the
characteristic Kitaev spin liquid features and the other showcasing ultraslow
fluctuations adhering to an Arrhenius activation law, indicative of glassy
characteristics. These findings suggest that Na2Co2TeO6, and eventually other
real-world Kitaev materials, may behave as quantum glass formers rather than
homogeneous quantum spin liquids when cooled.
