链间耦合对聚乙炔多链体系中电子极化子再激发态的影响

采用拓展紧束缚Su-Schrieffer-Heeger(SSH)模型,研究了链间耦合对反式聚乙炔多链体系中电子极化子再激发态的晶格位形、净电荷密度、局域能级波函数和态密度的影响.结果发现:对于两条链体系,当链间耦合很小(t⊥≤0.01 e V)时,注入到系统中的电子只会在第一条链上诱发产生一个晶格缺陷,形成电子极化子再激发态,这和单链体系是一致,而第二条链仍是二聚化基态.随着链间耦合的增大,第一条链上缺陷的局域度减少而第二条链上的缺陷局域度相应增加,直至两条链上的位形相同;对于多条链(5条链和6条链)体系,当耦合很小(t⊥≤0.05 e V)时,电子极化子再激发态也只会存在于一条链上,当链间耦合较强时,极化子再激发态会在链间层次性地扩展开来,并不会出现多条链位形相同;从两条链的能级图上可以看到随着链间耦合t⊥的增大,体系的带隙不断的增大和电子态密度显示的是完全吻合的,体系的导电性减弱.通过分析两条链体系在t⊥=0 e V和t⊥=0.1 e V的能级态密度,发现链间耦合越强,则中间局域能级的态密度越小,最后没有中间局域态.

The effect of interchain coupling on re-excitation state of electron polaron in multi-chains system of trans-polyacetylene

By using extend SSH Hamiltonian model, we investigated the effect of interchain coupling on the lattice configuration, net charge density, local level wave function and density of re-excitations state of electron polaron in multi-chains system of trans-polyacetylene. We found that the first chain induced a lattice defects and formed re-excitations state of electron polaron which is consistent with single chain system, and the second chain is dimerization ground state when interchain coupling is small(0.01eV) in double chains system. With the increase of interchain coupling, degree of local defects is reduced in the first chain and degree of local defects is increased in the second chain until two chains have the same configuration. For multiple chains system(five chains system and six chains system), re-excitation state of electron polaron will only exist in one chain when interchain coupling is small (0.05eV) and re-excitation state of electron polaron will extended between chains but does not appear the same configuration in each chain when interchain coupling is strong . We can see from the energy spectrum diagram of two chain system that the band gap increases constantly which are consistent with density of states, and electrical conductivity of the two chain system weakened. We also found that the stronger the interchain coupling, the smaller the local density of states (DOS) in the middle of energy spectrum , finally there is no localized energy level in band gap through the analysis of energy level density of states in two chain system with =0eV and =0.1eV.