Phase diagram of Na₂Co₂TeO_{6 ,} a Kitaev quantum spin liquid candidate in magnetic fields perpendicular to the honeycomb plane.

In 2006, Kitaev showed that a spin-1/2 system on a honeycomb lattice with bond-dependent anisotropic interactions can host non-Abelian anyons when an external magnetic field, perpendicular to the honeycomb lattice, gaps out the gapless quantum spin liquid. These anyons have the potential to be utilized for quantum computations. Cobaltates with a honeycomb lattice have been proposed as potential candidates to realize this phase. In this talk, we present a temperature-magnetic field phase diagram of a Kitaev spin liquid candidate Na₂Co₂TeO₆ measured up to 60 T perpendicular to the honeycomb plane. This phase diagram is constructed from magnetization and magnetocaloric effect measurements. Four magnetic transitions are observed consistently in both measurements. Magnetocaloric effect measurement result shows that the spin entropy continues to increase beyond 60 T, indicating that the spins are still not completely polarized at such a magnetic field, consistent with the extracted moment at 60 T being 1.6 µ_B/Co²⁺ compared to the 3 µ_B/Co²⁺ in-plane saturation moment [2]. We will discuss the potential nature of the observed phases and how our observation constraints existing and future theoretical proposals.



[1] Kitaev A. Annals of Physics, 321(1): 2-111 (2006).

[2] Zhang S, et al. Phys. Rev. B, 108(6): 064421 (2023).