The kagome-lattice materials promise emergence of Dirac fermions thanks to the special lattice geometry, which potentially realizes intriguing quantum topological states through various many-body interactions. The low-energy electromagnetic phenomena arising from such the Dirac fermions are expected to show the remarkable enhancement and, in certain conditions, to approach the universal responses, which, however, have remained elusive experimentally. Here, we show the resonantly enhanced magneto-optical response of massive Dirac fermions in kagome-lattice magnet TbMn₆Sn₆. The infrared magneto-optical spectroscopy reveals that the interband transition on massive Dirac bands significantly contributes to the observed resonance in the optical Hall conductivity. The analytical model expressed by a few band parameters reproduces the spectral characteristics of the resonance, which robustly produces almost 20 % of the quantized Hall conductance per one kagome layer even at room temperature. Our findings establish the general optical response of massive Dirac fermions, which is closely related to the universal electrodynamics in quantum anomalous Hall state.

由于特殊的晶格几何形状，戈薇晶格材料有望出现狄拉克费米子，它有可能通过各种多体相互作用实现有趣的量子拓扑态。由狄拉克费米子产生的低能电磁现象预计会表现出显着的增强，并且在某些条件下接近普遍响应，然而，这在实验上仍然难以捉摸。_{在这里，我们展示了戈薇晶格磁体 TbMn 6} Sn ₆中大量狄拉克费米子的共振增强磁光响应。红外磁光光谱表明，大狄拉克能带上的带间跃迁对光学霍尔电导率中观察到的共振有显着贡献。由几个带参数表示的分析模型再现了共振的光谱特性，即使在室温下，每一层 kagome 层也能稳健地产生近 20% 的量子化霍尔电导。我们的研究结果建立了大质量狄拉克费米子的一般光学响应，这与量子反常霍尔态的通用电动力学密切相关。