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RuCl₃ is thought to exhibit a strong Kitaev-type exchange interaction, but whether this interaction produces a spin liquid state with chiral Majorana edge modes is still unclear. Here, we present new measurements of the material’s thermal Hall conductivity down to He₃ temperatures. We observe a large, temperature-dependent signal that clearly differs from the temperature-independent form expected for Majorana fermions. Using the quantitative framework established by Matsumoto and Murakami [1], we show that this temperature-dependence can be fit to a bosonic model and that this fit produces values that are consistent with known parameters for RuCl₃.  How this result might be reconciled with other thermal transport reports will be discussed.  

[1] Matsumoto, R., Murakami, S. Phys. Rev. B 84, 184406 (2011).