Ultrafast Pathways of the Photoinduced Insulator–Metal Transition in a Low‐Dimensional Organic Conductor
Ultrafast Pathways of the Photoinduced Insulator–Metal Transition in a Low‐Dimensional Organic Conductor
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DOI：
10.1002/adma.201900652
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发表时间：
2019-03
影响因子：
29.4
通讯作者：
B. Smit;Florian Hüwe;N. Payne;O. Olaoye;I. Bauer;J. Pflaum;M. Schwoerer;H. Schwoerer
中科院分区：
文献类型：
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作者：
B. Smit;Florian Hüwe;N. Payne;O. Olaoye;I. Bauer;J. Pflaum;M. Schwoerer;H. Schwoerer
在功能有机材料中，低维分子晶体由于其可调的电子，磁性和结构基态而代表了一类有趣的固体。这项工作研究了Cu（Me，Br‐dicyanoquinonediimine）2单晶，这是一种电荷转移自由基离子盐，在低温下表现出Peierls绝缘体到金属的转变。超快电子衍射实验观测到光致相变时原子的集体运动，时间分辨率为1 ps。这些测量揭示了绝缘相的光致提升在整个晶体体积中在2 ps内发生，其中每个吸收光子的导带电子的外部量子效率大于20。这种巨大的协同系统，直接监测相变期间，伴随着特定的分子内运动。然而，只有对应于压力释放的额外的内部体积膨胀才允许长时间的金属状态被光学锁定。光学驱动Cu（DCNQI）2中结构Peierls转变的微观分子途径的识别突出了这些复杂功能材料对外部刺激的定制响应，这一特征使得高速光学传感和开关具有出色的信号响应度。
Among functional organic materials, low‐dimensional molecular crystals represent an intriguing class of solids due to their tunable electronic, magnetic, and structural ground states. This work investigates Cu(Me,Br‐dicyanoquinonediimine)2 single crystals, a charge transfer radical ion salt which exhibits a Peierls insulator‐to‐metal transition at low temperatures. The ultrafast electron diffraction experiments observe collective atomic motions at the photoinduced phase transition with a temporal resolution of 1 ps. These measurements reveal the photoinduced lifting of the insulating phase to happen within 2 ps in the entire crystal volume with an external quantum efficiency of conduction band electrons per absorbed photon of larger than 20. This huge cooperativity of the system, directly monitored during the phase transition, is accompanied by specific intramolecular motions. However, only an additional internal volume expansion, corresponding to a pressure relief, allows the metallic state for long times to be optically locked. The identification of the microscopic molecular pathways that optically drive the structural Peierls transition in Cu(DCNQI)2 highlights the tailored response to external stimuli available in these complex functional materials, a feature enabling high‐speed optical sensing and switching with outstanding signal responsivity.