标题： 在kagome超导体KV$_3$Sb$_5$中，格子驱动的电荷密度波在远高于凝聚温度的情况下发生波动 显示英文标题

标题： Fluctuated lattice-driven charge density wave far above the condensation temperature in kagome superconductor KV$_3$Sb$_5$

摘要： Kagome材料AV$_3$Sb$_5$展现出多种奇异的有序态，其中包括一种非传统的电荷密度波（CDW）。阐明CDW转变背后的机制对于揭示这些相之间的复杂相互作用至关重要。然而，由于系统内各种激发之间的交织相互作用，CDW的驱动因素仍然是一个有争议的话题。在这里，我们通过使用时间和角分辨光电子能谱来隔离超快电子相变，研究了KV$_3$Sb$_5$中的CDW转变。在临界光激发通量F$_c$下观察到了超快电子相变，而没有出现由CDW晶格畸变引起的能带折叠减少的现象。 在平衡加热条件下，这种折叠带一直持续到 150 K，远高于 CDW 凝结温度 T$_c$ = 78 K。值得注意的是，由泵浦诱导的在 F$_c$处的能带移动幅度与在 T$_c$温度下热效应引起的移动幅度相当。 这些发现表明，在KV$_3$Sb$_5$中，一种由晶格波动驱动的面内CDW（电荷密度波）在高于150K时出现，面外电子关联导致接近T$_c$时出现$2\times2 \times 2$CDW，为揭示AV$_3$Sb$_5$中电子和结构动力学之间的相互作用提供了关键见解。 显示英文摘要

摘要： The kagome material AV$_3$Sb$_5$ exhibits multiple exotic orders, including an unconventional charge density wave (CDW). Elucidating the underlying mechanism behind the CDW transition is crucial for unraveling the complex interactions among these phases. However, the driving force of the CDW remains a topic of debate due to the intertwined interactions among the system's various excitations. Here we investigated the CDW transition in KV$_3$Sb$_5$ by isolating the ultrafast electronic phase transition using time- and angleresolved photoemission spectroscopy. An ultrafast electronic phase transition was observed at a critical photoexcitation fluence, F$_c$, without reduction in CDW lattice-distortion-induced band folding. This folded band persisted up to 150 K under equilibrium heating, well above the CDW condensation temperature of T$_c$ = 78 K. Notably, the pump-induced band shifts at F$_c$ were comparable to those caused by thermal effects at T$_c$. These findings suggest that in KV$_3$Sb$_5$, a fluctuating lattice-driven in-plane CDW emerges above 150 K, with out-of-plane electronic correlations leading to the $2\times2 \times 2$ CDW near T$_c$, offering key insights into the interplay between the electronic and structural dynamics in AV$_3$Sb$_5$.