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arXiv 1106.2648cond-mat.str-el
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二聚体莫特绝缘体到金属的光激发能量依赖跃迁途径

Photoexcitation-Energy-Dependent Transition Pathways from a Dimer Mott Insulator to a Metal

Kenji Yonemitsu, Satoshi Miyashita, Nobuya Maeshima

摘要:

在数值求解含时薛定谔方程的精确多体波函数的基础上,对二维四分之三填充扩展Peierls-哈伯德模型的光诱导二聚体-Mott绝缘体-金属跃迁的泵浦光子能量依赖途径进行了理论研究.当利用二聚体内部的分子自由度时,光激发可以减弱有效相互作用或增加光载流子的密度。在有机二聚体莫特绝缘体体$ κ$ -(BEDT-TTF)$_2$ Cu[N(CN)$_2$ ]Br中,二聚体内和二聚体间电荷转移激发具有彼此重叠的宽带。即使在这种不利的情况下,光致电导率的变化在很大程度上取决于泵浦光子的能量,确认最近实验观察到的两个途径。通过计算有效相互作用的调制和参与低能光激发的载流子数,阐明了每条路径的特性。泵浦光子能量依赖的途径被证实是实现从发现,虽然有效的相互作用总是和缓慢减弱,载流子的引入是敏感的泵浦光子能量和进行得更快。

英文摘要:

We theoretically study pump-photon-energy-dependent pathways of a photoinduced dimer-Mott-insulator-to-metal transition, on the basis of numerical solutions to the time-dependent Schrödinger equation for the exact many-body wave function of a two-dimensional three-quarter-filled extended Peierls-Hubbard model. When molecular degrees of freedom inside a dimer are utilized, photoexcitation can weaken the effective interaction or increase the density of photocarriers. In the organic dimer Mott insulator, $ κ$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br, the intradimer and the interdimer charge-transfer excitations have broad bands that overlap with each other. Even in this disadvantageous situation, the photoinduced conductivity change depends largely on the pump photon energy, confirming the two pathways recently observed experimentally. The characteristic of each pathway is clarified by calculating the modulation of the effective interaction and the number of carriers involved in low-energy optical excitations. The pump-photon-energy-dependent pathways are confirmed to be realized from the finding that, although the effective interaction is always and slowly weakened, the introduction of carriers is sensitive to the pump-photon energy and proceeds much faster.

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