Density-matrix renormalization-group calculations of excited states of linear polyenes
Density-matrix renormalization-group calculations of excited states of linear polyenes
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DOI：
10.1103/physrevb.63.195108
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发表时间：
2001-05-15
影响因子：
3.7
通讯作者：
Lavrentiev, MY
中科院分区：
文献类型：
--
作者：
Barford, W;Bursill, RJ;Lavrentiev, MY
我们提出了绝热近似内线性多烯的 Pariser-Parr-Pople-Peierls 模型的密度矩阵重整化群计算。我们计算了长链上各种激发的垂直和松弛跃迁能量以及松弛几何形状。三重态 (1 B-3(u)+) 和偶宇称单重态 (2 (1)A(g)(+)) 态具有 2-孤子和 4-孤子形式。分别具有较大的弛豫能量。偶极允许态(1 B-1(u)-)形成激子极化子，并且具有非常小的弛豫能。 2 (1)A(g)(+) 态的弛豫能低于 1 B-1(u)- 态的弛豫能。我们观察到 2 (1)A(g)(+) 态的孤子-反孤子对之间存在吸引力。计算的激发能与多烯低聚物的观测值非常吻合；与聚乙炔薄膜的一致性不太好，我们对差异的可能来源进行评论。解释光诱导吸收。自旋-自旋相关函数表明，不成对的自旋与几何孤子位置一致。我们研究电子-电子相互作用和电子-晶格耦合在确定激发能和孤子结构中的作用。电子相互作用在确定基态二聚和激发态跃迁能量中起着关键作用。
We present density-matrix renormalization-group calculations of the Pariser-Parr-Pople-Peierls model of linear polyenes within the adiabatic approximation. We calculate the vertical and relaxed transition energies, and relaxed geometries for various excitations on long chains. The triplet (1 B-3(u)+) and even-parity singlet (2 (1)A(g)(+)) states have a 2-soliton and 4-soliton forms. respectively, both with large relaxation energies. The dipole-allowed (1 B-1(u)-) state forms an exciton-polaron, and has a very small relaxation energy. The relaxed energy of the 2 (1)A(g)(+) state lies below that of the 1 B-1(u)- state. We observe an attraction between the soliton-antisoliton pairs in the 2 (1)A(g)(+) state. The calculated excitation energies agree well with the observed values for polyene oligomers; the agreement with polyacetylene thin films is less good, and we comment on the possible sources of the discrepancies. The photoinduced absorption is interpreted. The spin-spin correlation function shows that the unpaired spins coincide with the geometrical soliton positions. We study the roles of electron-electron interactions and electron-lattice coupling in determining the excitation energies and soliton structures. Electronic interactions play the key role in determining the ground-state dimerization and the excited-state transition energies.