AI 中文总结
本研究采用机器学习力场实时模拟1T-TaS₂的CDW相变，揭示其两步机制：200K以上SoD簇平移、350K附近SoD畸变坍缩，为CDW两步模型提供微观支持，可用于解释1T-TaS₂的光诱导隐藏相等现象。
AI 中文摘要
块状1T-TaS₂的电荷密度波（CDW）由大卫星（Star-of-David, SoD）簇构成，这些簇排列成√13×√13超晶格，其熔化过程分为两步，伴随电阻率发生数量级变化。由于相关动力学过程的长度和时间尺度超出了从头算分子动力学的能力范围，这两步是通过SoD振幅坍缩还是SoD晶格重排发生的问题仍未解决。本文使用基于第一性原理数据训练的机器学习力场，对CDW相变进行实时追踪，可覆盖1404原子超胞，模拟时长5纳秒。研究发现两步相变的机制截然不同：在200K以上，SoD簇通过在偏移中心处短暂溶解并重新形成而发生相干平移，该变形-形成过程保留了局部SoD振幅，同时使层间堆垛无序化并成核畴壁；仅在350K附近，SoD畸变本身才发生坍缩。这些结果为近期提出的CDW两步模型提供了微观支持，并为解释1T-TaS₂中的光诱导隐藏相和腔修饰相变温度提供了框架。
英文摘要
The charge-density wave (CDW) of bulk 1T-TaS2 is built from Star-of-David (SoD) clusters tiling a sqrt{13} x sqrt{13} superlattice, and it melts through a two-step sequence accompanied by order-of-magnitude changes in resistivity. Whether these steps proceed by collapse of the SoD amplitude or by rearrangement of the SoD lattice has remained unresolved, because the relevant dynamics occur on length and time scales beyond the reach of ab initio molecular dynamics. Here we follow the CDW transitions in real time using a machine-learning force field trained on first-principles data, giving access to 1404-atom supercells over 5 ns. The two steps are mechanistically distinct. Above 200 K, SoD clusters translate coherently by transiently dissolving and re-forming about shifted centers, a deformation-formation process that preserves the local SoD amplitude while randomizing the interlayer stacking order and nucleating domain walls. Only near 350 K does the SoD distortion itself collapse. These results provide microscopic support for the recently proposed two-step model of the CDW transition and offer a framework for interpreting light-induced hidden phases and cavity-modified transition temperatures in 1T-TaS2.
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