Photoinduced Switching to Metallic States in the Two-Dimensional Organic Mott Insulator Dimethylphenazine-Tetrafluorotetracyanoquinodimethane with Anisotropic Molecular Stacks
Photoinduced Switching to Metallic States in the Two-Dimensional Organic Mott Insulator Dimethylphenazine-Tetrafluorotetracyanoquinodimethane with Anisotropic Molecular Stacks
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具有各向异性分子堆栈的二维有机莫特绝缘体二甲基吩嗪-四氟四氰基对醌二甲烷中光诱导转变为金属态
DOI：
10.1103/physrevb.91.245140
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
and H. Okamoto
中科院分区：
文献类型：
--
作者：
H. Matsuzaki;M. Ohkura;Y. Ishige;Y. Nogami;and H. Okamoto
利用飞秒激光泵浦-探测反射光谱研究了有机电荷转移（CT）复合物：5，10-二氢-5，10-二甲基吩嗪（D），给体分子：2，3，5，6-四氟-7，7，8，8-四氰基醌二甲烷（A）]的光诱导相变.这是一种离子化合物，具有独特的二维（2D）分子排列;相同的A（或D）分子沿[100]方向沿着排列，A和D分子沿[111]方向沿着交替排列。它导致了强各向异性的二维电子结构。该化合物在122 K时发生结构和磁性相变，低于此温度时，两个相邻分子沿[100]和[111]方向沿着二聚化。我们证明了两种光致相变发生的飞秒激光脉冲的照射;在高温晶格均匀相，准一维（1D）金属态沿着AA（DD）堆栈产生，在低温晶格二聚相，准二维金属态最初产生和分子二聚随后释放。由DA堆组成的混合堆CT化合物通常是处于基态的绝缘体或半导体。这里，演示了DA堆叠中的这种动态金属化。二聚化的释放驱动了几种相干振荡，这些振荡在晶格二聚化相的稳定中起着重要作用。这些光致相变的机制进行了讨论的各向异性带宽和分子二聚化的大小沿沿着两个不同方向的分子堆叠。
A photoinduced phase transition was investigated in an organic charge-transfer (CT) complex: 5,10-dihydro-5,10-dimethylphenazine, donor (D) molecule;: 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, acceptor (A) molecule] by means of femtosecond pump-probe reflection spectroscopy. This is an ionic compound and has a peculiar two-dimensional (2D) molecular arrangement; the same A (or D) molecules arrange along the [100] direction, and A and D molecules alternately arrange along the [111] direction. It results in a strongly anisotropic two-dimensional electronic structure. This compound shows a structural and magnetic phase transition at 122 K below which the two neighboring molecules are dimerized along both the [100] and [111] directions. We demonstrate that two kinds of photoinduced phase transitions occur by irradiation of a femtosecond laser pulse; in the high-temperature lattice-uniform phase, a quasi-one-dimensional (1D) metallic state along the AA(DD) stack is generated, and in the low-temperature lattice-dimerized phase, a quasi-2D metallic state is initially produced and molecular dimerizations are subsequently released. Mixed-stack CT compounds consisting of DA stacks are generally insulators or semiconductors in the ground state. Here, such a dynamical metallization in the DA stack is demonstrated. The release of the dimerizations drives several kinds of coherent oscillations which play an important role in the stabilization of the lattice-dimerized phase. The mechanisms of those photoinduced phase transitions are discussed in terms of the magnitudes of the anisotropic bandwidths and molecular dimerizations along two different directions of the molecular stacks.