Ultrafast formation of topological defects in a two-dimensional charge density wave
Ultrafast formation of topological defects in a two-dimensional charge density wave
复制标题
DOI：
10.1038/s41567-023-02279-x
复制
发表时间：
2022-11
期刊：
影响因子：
19.6
通讯作者：
Yun Cheng;A. Zong;Lijun Wu;Q. Meng;Weicong Xia;Fengfeng Qi;P. Zhu;Xiaoqun Zou;Tao Jiang;Yanfeng Guo;Jasper van Wezel;A. Kogar;M. Zuerch;Jie Zhang;Yimei Zhu;D. Xiang
中科院分区：
文献类型：
--
作者：
Yun Cheng;A. Zong;Lijun Wu;Q. Meng;Weicong Xia;Fengfeng Qi;P. Zhu;Xiaoqun Zou;Tao Jiang;Yanfeng Guo;Jasper van Wezel;A. Kogar;M. Zuerch;Jie Zhang;Yimei Zhu;D. Xiang
拓扑缺陷在经历非绝热转变的动力学系统中起着核心作用。在固体中，由于飞秒激光激发的拓扑缺陷引起了越来越多的兴趣，这不仅是因为它们是理解相变的关键，而且还因为它们可以产生各种在热平衡中不可访问的隐藏顺序。尽管这些缺陷在非平衡系统中经常发生，但它们在固体中出现的速度以及在如此快的时间尺度下产生缺陷的一般途径的基本限制仍然是悬而未决的问题。在这里，我们应用超快电子衍射研究的倒数空间签名的瞬态缺陷在一个二维的电荷密度波，同时测量缺陷和声子动力学产生的缺陷形成的飞秒制度的微观视图。我们发现，一维畴壁产生以及在1 ps以下的光激发，在此期间的缺陷生长是不受序参数的幅度，但介导的纵向光学声子的非热人口。我们的工作提供了一个框架的拓扑缺陷，耦合到特定的集体模式，这将被证明是有用的相关材料的非平衡相的动态控制的超快工程。
Topological defects play a central role in dynamical systems undergoing a non-adiabatic transition. In solids, topological defects as a result of femtosecond laser excitation have attracted increasing interest not only because they are key to understanding phase transitions but also because they can generate a variety of hidden orders that are not accessible in thermal equilibrium. Despite the common occurrence of these defects in a non-equilibrium system, the fundamental limit on how fast they can emerge in solids and the generic pathway for defect creation at such fast timescales have remained open questions. Here we apply ultrafast electron diffraction to study the reciprocal-space signatures of transient defects in a two-dimensional charge density wave, where simultaneous measurements of both defect and phonon dynamics yield a microscopic view of defect formation in the femtosecond regime. We find that one-dimensional domain walls are generated well within 1 ps following photoexcitation, during which the defect growth is not dictated by the amplitude of the order parameter, but is mediated by a non-thermal population of longitudinal optical phonons. Our work provides a framework for the ultrafast engineering of topological defects that are coupled to specific collective modes, which will prove useful for the dynamical control of non-equilibrium phases in correlated materials.