Zhang Jin, Lian Chao, Guan Mengxue, Ma Wei, Fu Huixia, Guo Haizhong, Meng Sheng
Beijing National Laboratory for Condensed Matter Physics , Institute of Physics, Chinese Academy of Sciences , Beijing 100190 , P. R. China.
School of Physical Sciences , University of Chinese Academy of Sciences , Beijing 100049 , P. R. China.
Nano Lett. 2019 Sep 11;19(9):6027-6034. doi: 10.1021/acs.nanolett.9b01865. Epub 2019 Aug 19.
Photoexcitation is a powerful means in distinguishing different interactions and manipulating the states of matter, especially in charge density wave (CDW) materials. The CDW state of 1-TaS has been widely studied experimentally mainly because of its intriguing laser-induced ultrafast responses of electronic and lattice subsystems. However, the microscopic atomic dynamics and underlying electronic mechanism upon photoexcitation remain unclear. Here, we demonstrate photoexcitation induced ultrafast dynamics of CDW in 1-TaS using time-dependent density functional theory molecular dynamics. We discover a novel collective oscillation mode between the CDW state and a transient state induced by photodoping, which is significantly different from thermally induced phonon mode and attributed to the modification of the potential energy surface from laser excitation. In addition, our finding validates nonthermal melting of CDW induced at low light intensities, supporting that conventional hot electron model is inadequate to explain photoinduced dynamics. Our results provide a deep insight into the coherent electron and lattice quantum dynamics during the formation and excitation of CDW in 1-TaS.
光激发是区分不同相互作用和操纵物质状态的有力手段，特别是在电荷密度波（CDW）材料中。1-TaS的CDW态已得到广泛的实验研究，主要是因为其有趣的激光诱导电子和晶格子系统的超快响应。然而，光激发下的微观原子动力学和潜在电子机制仍不清楚。在此，我们使用含时密度泛函理论分子动力学证明了光激发诱导的1-TaS中CDW的超快动力学。我们发现了一种由光掺杂诱导的CDW态与瞬态之间的新型集体振荡模式，它与热诱导声子模式显著不同，且归因于激光激发导致的势能面的改变。此外，我们的发现验证了低光强下诱导的CDW的非热熔化，支持传统的热电子模型不足以解释光诱导动力学。我们的结果为深入了解1-TaS中CDW形成和激发过程中的相干电子和晶格量子动力学提供了依据。
