Scaling behavior and giant field-enhancement of the thermal conductivity in the honeycomb antiferromagnet BaCo2(AsO4)2

The layered honeycomb material BaCo₂ (AsO₄) ₂ (BCAO) is of topical interest because its magnetic state is related to that of the Kitaev magnet -RuCl₃. Using thermal transport to probe how magnetic excitations interact with phonons, we have uncovered an unusually large enhancement of the thermal conductivity ₗₗ in an in-plane magnetic field H. Just above the N\'eel temperature T ₍, a field of 13 T increases ₗₗ by a factor (211), much larger than reported previously in any magnetic insulator. Interestingly, ₗₗ (H, T) exhibits a scaling behavior in the entire magnetically disordered region that surrounds the ordered zigzag state.