Quantum dynamics of exciton transport in semiconducting polymer chains: Coherent or diffusive?
Irene Burghardt, Goethe University Frankfurt
Intra-chain exciton transport in organic molecular materials is often described by the Frenkel-Holstein (FH) Hamiltonian that admits incoherent hopping or coherent transport dynamics in different parameter regimes. To bridge the gap to a molecular-level description, we describe a protocol that generates a one-to-one mapping of supermolecular oligomer potential energy surfaces onto a generalized FH Hamiltonian. When combined with efficient quantum dynamical simulations using the multi-layer multi-configuration time-dependent Hartree (ML-MCTDH) method, this approach provides unbiased insight into the elementary mechanism of exciton migration. This lecture presents case studies of polythiophene and poly(para-phenylene vinylene) type materials [1-3] where a coherent transport regime is observed, showing that "excitons surf along conjugated polymer chains" [4]. The dynamics acquires partial hopping character if static disorder becomes prominent and Anderson localization sets in. Special emphasis is placed on the interplay of delocalization, trapping, and thermal activation due to soft modes such as ring torsions.
[1] R. Binder, I. Burghardt, Faraday Discuss. 221, 406 (2020).
[2] F. Di Maiolo, D. Brey, R. Binder, I. Burghardt, J. Chem. Phys. 153, 184107 (2020).
[3] R. Binder, D. Lauvergnat, I. Burghardt, Phys. Rev. Lett., 120, 227401 (2018).
[4] J.L. Bredas, R. Silbey, Science 323, 348 (2009).