论文标题
多烯和类胡萝卜素的黑暗状态的理论
Theory of the Dark State of Polyenes and Carotenoids
论文作者
论文摘要
开发了一种理论来描述多烯和类胡萝卜素的单线暗状态（通常标记为S1或2AG）。该理论假定原则上，该状态是单线三重态和奇怪的电荷转移激子的线性组合。至关重要的是，这些组件仅在三胞胎对占据相邻的二聚体时仅夫妇，因此三胞胎之间的电子转移会产生最近的邻居电荷转移激发。这种局部耦合稳定了2AG状态，并引起三胞胎之间最近的邻居吸引力。另外，由于激子中的电子孔吸引力，电子孔对占据相邻二聚体的概率增加增强了三重态 - 三个二线吸引力：三重态对“奴隶”对向电荷转移 - 转移ixciton。该理论还预测，随着库仑相互作用的增加，2Ag状态从主要的奇数荷荷电荷转移激子状态演变为具有三重态特征的一小部分，转变为主要由具有一些激子特征的三胞胎对组成的状态。在临界库仑相互作用之上，三重态和电荷转移激子子空间的脱钩，使得2AG状态完全由一个无结合的自旋相关的三重态组成。该理论的预测在质量上与Pariser-Parr-Pople（或扩展Hubbard）模型的高级密度基质重新归一化组计算一致。
A theory is developed to describe the singlet dark state (usually labeled S1 or 2Ag) of polyenes and carotenoids. The theory assumes that in principle this state is a linear combination of a singlet triplet-pair and an odd-parity charge-transfer exciton. Crucially, these components only couple when the triplet-pair occupies neighboring dimers, such that an electron transfer between the triplets creates a nearest-neighbor charge-transfer excitation. This local coupling stabilises the 2Ag state and induces a nearest neighbor attraction between the triplets. In addition, because of the electron-hole attraction in the exciton, the increased probability that the electron-hole pair occupies neighboring dimers enhances the triplet-triplet attraction: the triplet pair is `slaved' to the charge-transfer exciton. The theory also predicts that as the Coulomb interaction is increased, the 2Ag state evolves from a predominately odd-parity charge-transfer exciton state with a small component of triplet-pair character to a state predominately composed of a triplet-pair with some exciton character. Above a critical Coulomb interaction there is a decoupling of the triplet-pair and charge-transfer exciton subspaces, such that the 2Ag state becomes entirely composed of an unbound spin-correlated triplet pair. The predictions of this theory are qualitatively consistent with high-level density matrix renormalization group calculations of the Pariser-Parr-Pople (or extended Hubbard) model.
