Fig. 1: Thermal conductivity of Na₂Co₂TeO₆ and the impact of the in-plane magnetic fields.

a In-plane thermal conductivity of five Na₂Co₂TeO₆ crystals without magnetic field. The thermal gradient (∇T) was set ∥ zigzag for Sample#1 and Sample#4, and ∥ armchair for the other three samples. By extrapolating the data to T = 0 K, a residual linear term (κ/T∣_T→0) can be resolved for all five κ/T(T) curves, especially clear for Sample#1, as indicated by the dashed blue line. b The field dependence of the κ/T(T) curves for Sample#1, focusing on the small field limit which covers a small portion of (c), the full field dependence of the κ/T(T) curves, as indicated by the gray background. At T = 1 K, the κ of Sample#1 experience a 70-fold increase from B = 0 T to the saturation field. d The κ/T(T) curves display a typical phononic ∝ T^α behavior with α = 1.5 at high enough fields. The field direction does not affect the saturated κ/T(T) curves.