Density matrix renormalization group study of conjugated polymers with transverse π-conjugation

We report accurate numerical studies of excited state orderings in long hypothetical π-conjugated oligomers in which the hydrogen atoms of transpolyacetylene are replaced with conjugated side groups, within modified Hubbard models. There exists a range of the bare Coulomb repulsion for which the excited state ordering is conducive to photoluminescence in the substituted systems, even as this ordering is opposite in the unsubstituted polyenes of the same lengths. Our work provides motivation to study real π-conjugated polymers with transverse conjugation and small optical gaps.