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

Haoran Liu; Shaofeng Duan; Xiangqi Liu; Zhihua Liu; Shichong Wang; Lingxiao Gu; Jiongyu Huang; Wenxuan Yang; Jianzhe Liu; Dong Qian; Yanfeng Guo; Wentao Zhang

doi:10.1016/j.scib.2025.02.018

arXiv · 2504.16620

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

Haoran Liu·Shaofeng Duan·Xiangqi Liu·Zhihua Liu·Shichong Wang·Lingxiao Gu·Jiongyu Huang·Wenxuan Yang·Jianzhe Liu·Dong Qian·Yanfeng Guo·Wentao Zhang

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Abstract

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$_5$.

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Haoran Liu, Shaofeng Duan, Xiangqi Liu, Zhihua Liu, Shichong Wang, Lingxiao Gu, Jiongyu Huang, Wenxuan Yang, Jianzhe Liu, Dong Qian, Yanfeng Guo, Wentao Zhang. 2025-04-23. Fluctuated lattice-driven charge density wave far above the condensation temperature in kagome superconductor KV$_3$Sb$_5$. https://doi.org/10.1016/j.scib.2025.02.018

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