Explorations of new optical switching phenomena in strongly correlated electron systems

强相关电子系统中新光开关现象的探索

基本信息

批准号：
16340086
负责人：
OKAMOTO Hiroshi
金额：
$ 10.43万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

In this research project, we aimed to explore new kinds of photoinduced phase transitions (optical switching phenomena) in which transport, optical and magnetic properties are largely changed by lights and to clarify their physical mechanisms. The main achievements are summarized below.?Z We found an ultrafast photoinduced insulator-metal transition in a two-dimensional Mott insulator of an organic charge-transfer compound,(M_2P-F_4TCNQ). From the detailed analyses of the transient reflectivity spectra and their time dependences, we revealed that the decay time of the photoinduced metallic state is very fast, being 0.4 ps, and the metallic state is two-dimensional in nature. Such a fast decay is considered characteristic of two-dimensional correlated electron systems.?Z We found an ultrafast photoinduced insulator-metal transition in a one-dimensional Mott insulator of an organic charge-transfer compound,(BEDTTTF-F_2TCNQ). The important feature of this transition is that a metallic behavior was observed even for a very weak excitation photon density (<0.003 photon/site). We concluded that such a formation of a metallic state by a weak excitation is attributable to the spin-charge separation characteristic of 1D correlated electron systems.?Z We found an ultrafast photoinduced charge density wave (CDW)-Mott Hubbard transition in a typical transition metal compound with a one-dimensional correlated electron system, an iodine-bridged platinum compound. Werevealed that the efficiency of the transition is very high (ca. 70 Pt sites per photon) and that a CDW to metal transition occurs by a strong excitation. Namely, photoinduced phase transitions among three phases (CDW, Mott-Hubbard, metal) are possible in this compound.Thus, in this project, we have succeeded in exploring new photoinduced phase transitions and achieved the clarifications of their physical mechanisms.

在该研究项目中，我们旨在探索新型的光诱导的相变（光学切换现象），其中传输，光学和磁性特性在很大程度上被灯光变化并澄清其物理机制。主要成就在下面总结了。？Z我们在有机电荷转移化合物（M_2P-F_4TCNQ）的二维Mott绝缘子中发现了超快光诱导的绝缘子 - 金属过渡。从瞬态反射率谱及其时间依赖的详细分析中，我们透露，光诱导的金属状态的衰减时间非常快，为0.4 ps，金属状态本质上是二维的。这种快速的衰减被认为是二维相关电子系统的特征。？这种过渡的重要特征是，即使对于非常弱的激发光子密度（<0.003光子/位点），也观察到金属行为。 We concluded that such a formation of a metallic state by a weak excitation is attributable to the spin-charge separation characteristic of 1D correlated electron systems.?Z We found an ultrafast photoinduced charge density wave (CDW)-Mott Hubbard transition in a typical transition metal compound with a one-dimensional correlated electron system, an iodine-bridged platinum compound.被视为过渡的效率很高（每光子70分），并且CDW向金属转变是通过强激发发生的。也就是说，在该化合物中可能有三个阶段（CDW，Mott-Hubbard，Metal）之间的光诱导的相变。在此项目中，我们成功地探索了新的光诱导的相变并实现了其物理机制的澄清。