Quasi-two-dimensional transition-metal dichalcogenides are a key platform for exploring emergent nanoscale phenomena arising from complex interactions. Access to the underlying degrees-of-freedom on their natural time scales motivates the use of advanced ultrafast probes sensitive to self-organised atomic-scale patterns. Here, we report the ultrafast investigation of TaTe₂, which exhibits unique charge and lattice trimer order characterised by a transition upon cooling from stripe-like chains into a (3 × 3) superstructure of trimer clusters. Utilising MeV-scale ultrafast electron diffraction, we capture the photo-induced TaTe₂ structural dynamics – exposing a rapid ≈ 1.4 ps melting of its low-temperature ordered state followed by recovery via thermalisation into a hot cluster superstructure. Density-functional calculations indicate that the initial quench is triggered by intra-trimer Ta charge transfer which destabilises the clusters, unlike melting of charge density waves in other TaX₂ compounds. Our work paves the way for further exploration and ultimately rapid optical and electronic manipulation of trimer superstructures.

准二维过渡金属二硫属化物是探索复杂相互作用产生的新兴纳米级现象的关键平台。在自然时间尺度上获得潜在的自由度促使使用对自组织原子尺度模式敏感的先进超快探针。在这里，我们报告了对 TaTe ₂的超快研究，它表现出独特的电荷和晶格三聚体顺序，其特征在于冷却时从条状链转变为三聚体簇的 (3 × 3) 超结构。利用 MeV 级超快电子衍射，我们捕获了光诱导的 TaTe ₂结构动力学——暴露其低温有序状态的快速约 1.4 ps 熔化，然后通过热化恢复到热簇上层结构。密度泛函计算表明初始猝灭是由三聚体内部的 Ta 电荷转移触发的，这使团簇不稳定，这与其他 TaX ₂化合物中的电荷密度波的熔化不同。我们的工作为进一步探索和最终快速光学和电子操纵三聚体上层结构铺平了道路。