Guzelturk Burak, Portner Joshua, Ondry Justin, Ghanbarzadeh Samira, Tarantola Mia, Jeong Ahhyun, Field Thomas, Chandler Alicia M, Wieman Eliza, Hopper Thomas R, Watkins Nicolas E, Yu Jin, Cheng Xinxin, Lin Ming-Fu, Luo Duan, Kramer Patrick L, Shen Xiaozhe, Reid Alexander H, Borkiewicz Olaf, Ruett Uta, Zhang Xiaoyi, Lindenberg Aaron M, Ma Jihong, Schaller Richard D, Talapin Dmitri V, Cotts Benjamin L
X-ray Science Division, Argonne National Laboratory, Lemont, IL, 60527, USA.
Department of Chemistry, James Franck Institute, and Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, 60637, USA.
Adv Mater. 2025 Jan;37(4):e2414196. doi: 10.1002/adma.202414196. Epub 2024 Nov 25.
Symmetry control is essential for realizing unconventional properties, such as ferroelectricity, nonlinear optical responses, and complex topological order, thus it holds promise for the design of emerging quantum and photonic systems. Nevertheless, fast and reversible control of symmetry in materials remains a challenge, especially for nanoscale systems. Here, reversible symmetry changes are unveiled in colloidal lead chalcogenide quantum dots on picosecond timescales. Using a combination of ultrafast electron diffraction and total X-ray scattering, in conjunction with atomic-scale structural modeling and first-principles calculations, it is revealed that symmetry-broken lead sulfide quantum dots restore to a centrosymmetric phase upon photoexcitation. The symmetry restoration is driven by photoexcited electronic carriers, which suppress lead off-centering for about 100 ps. Furthermore, the change in symmetry is closely correlated with the electronic properties, and the bandgap transiently red-shifts in the symmetry-restored quantum dots. Overall, this study elucidates reversible symmetry changes in colloidal quantum dots, and more broadly defines a new methodology to optically control symmetry in nanoscale systems on ultrafast timescales.
对称性控制对于实现非传统特性至关重要，例如铁电性、非线性光学响应和复杂的拓扑序，因此它为新兴量子和光子系统的设计带来了希望。然而，材料中对称性的快速和可逆控制仍然是一个挑战，特别是对于纳米级系统。在此，在皮秒时间尺度上揭示了胶体硫属铅化物量子点中的可逆对称性变化。通过结合超快电子衍射和全X射线散射，以及原子尺度结构建模和第一性原理计算，发现对称性破缺的硫化铅量子点在光激发后恢复到中心对称相。对称性恢复由光激发的电子载流子驱动，这些载流子抑制铅的离中心约100皮秒。此外，对称性的变化与电子特性密切相关，并且在对称性恢复的量子点中带隙会瞬间红移。总体而言，这项研究阐明了胶体量子点中的可逆对称性变化，并更广泛地定义了一种在超快时间尺度上光学控制纳米级系统对称性的新方法。
