Counting the number of excited states in organic semiconductor systems using topology.

@article{Catanzaro2015CountingTN,
  title={Counting the number of excited states in organic semiconductor systems using topology.},
  author={Michael J. Catanzaro and Tian Shi and Sergei Tretiak and Vladimir Y. Chernyak},
  journal={The Journal of chemical physics},
  year={2015},
  volume={142 8},
  pages={
          084113
        }
}
Exciton scattering theory attributes excited electronic states to standing waves in quasi-one-dimensional molecular materials by assuming a quasi-particle picture of optical excitations. The quasi-particle properties at branching centers are described by the corresponding scattering matrices. Here, we identify the topological invariant of a scattering center, referred to as its winding number, and apply topological intersection theory to count the number of quantum states in a quasi-one… 

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