Heavy-fermion systems represent one of the paradigmatic strongly correlated states of matter^1,2,3,4,5. They have been used as a platform for investigating exotic behaviour ranging from quantum criticality and non-Fermi liquid behaviour to unconventional topological superconductivity^{4,5,6,7,8,9,10,11,12}. The heavy-fermion phenomenon arises from the exchange interaction between localized magnetic moments and conduction electrons leading to Kondo lattice physics, and represents one of the long-standing open problems in quantum materials³. In a Kondo lattice, the exchange interaction gives rise to a band with heavy effective mass. This intriguing phenomenology has so far been realized only in compounds containing rare-earth elements with 4f or 5f electrons^1,4,13,14. Here we realize a designer van der Waals heterostructure where artificial heavy fermions emerge from the Kondo coupling between a lattice of localized magnetic moments and itinerant electrons in a 1T/1H-TaS₂ heterostructure. We study the heterostructure using scanning tunnelling microscopy and spectroscopy and show that depending on the stacking order of the monolayers, we can reveal either the localized magnetic moments and the associated Kondo effect, or the conduction electrons with a heavy-fermion hybridization gap. Our experiments realize an ultimately tunable platform for future experiments probing enhanced many-body correlations, dimensional tuning of quantum criticality and unconventional superconductivity in two-dimensional artificial heavy-fermion systems^15,16,17.

^{重费米子系统代表了物质1,2,3,4,5}的一种典型的强相关状态。它们已被用作研究奇异行为的平台，范围从量子临界性和非费米液体行为到非常规拓扑超导性^{4,5,6,7,8,9,10,11,12}。^{重费米子现象源于局部磁矩和传导电子之间的交换相互作用，导致近藤晶格物理学，代表了量子材料3}中长期存在的开放性问题之一。在 Kondo 晶格中，交换相互作用产生了具有重有效质量的带。到目前为止，这种有趣的现象只在含有 4 f 的稀土元素的化合物中得到了实现。或 5 个f电子^1,4,13,14。在这里，我们实现了设计师范德瓦尔斯异质结构，其中人造重费米子从 1T/1H-TaS 2 中局域磁矩晶格与流动电子之间的 Kondo 耦合中_出现异质结构。我们使用扫描隧道显微镜和光谱学研究异质结构，并表明根据单层的堆叠顺序，我们可以揭示局部磁矩和相关的 Kondo 效应，或具有重费米子杂化间隙的传导电子。我们的实验实现了一个最终可调的平台，用于未来实验探索增强的多体相关性、量子临界的维调和二维人工重费米子系统 15,16,17 中的非常规超导^性。