Dynamical Simulations of Polaron Transport in Conjugated Polymers with the Inclusion of Electron−Electron Interactions

Abstract

Dynamical simulations of polaron transport in conjugated polymers in the presence of an external time-dependent electric field have been performed within a combined extended Hubbard model (EHM) and Su-Schrieffer-Heeger (SSH) model. Nearly all relevant electron-phonon and electronelectron interactions are fully taken into account by solving the time-dependent Schrödinger equation for the π-electrons and the Newton's equation of motion for the backbone monomer displacements by virtue of the combination of the adaptive time-dependent density matrix renormalization group (TDDMRG) and classical molecular dynamics (MD). We find that after a smooth turn-on of the external electric field the polaron is accelerated at first and then moves with a nearly constant velocity as one entity consisting of both the charge and the lattice deformation. An ohmic region (3 mV/Å ≤ E 0 ≤ 9 mV/Å) where the stationary velocity increases linearly with the electric field strength is observed for the case of U =2.0 eV and V =1.0 eV. The maximal velocity is well above the speed of sound. Below 3 mV/Å the polaron velocity increases nonlinearly and in high electric fields with strength E 0 ≥ 10.0 mV/Å the polaron will become unstable and dissociate. The relationship between electron-electron interaction strengths and polaron transport is also studied in detail. We find that the the on-site Coulomb interactions U will suppress the polaron transport and small nearest-neighbor interactions V values are also not beneficial to the polaronic motion while large V values favor the polaron transport.

Effect of Electron−Electron Interactions on the Charge Carrier Transitions intrans-Polyacetylene

“…[36][37][38][39] All our numerical results presented in this work are well-converged values calculated with ǫ ρ = 1.0 × 10 −7 and ∆t=0.05 fs.…”

“…The main idea of this method is to evolve the π-electron part by the adaptive TDDMRG and move the backbone part by classical MD iteratively and nonadiabatically to include nearly all relevant electron-phonon and electron-electron interactions. Details about such the combined TDDMRG/MD method can be found in the recent papers [36][37][38][39].…”

Long-range Coulomb interaction effects on polarons in conjugated polymers

“…The more localized a polaron is the larger is its effective mass. As a result, the saturated velocity decreases monotonically with increasing U, which is in agreement with the results obtained by other theoretical calculations [16][17][18]. Therefore, we can conclude that the on-site Coulomb interaction tends to reduce the speed of a polaron.…”

“…The polaron moves with a supersonic velocity, about four times the velocity of sound in the small U limit, and approaches the velocity of sound for large U [17]. Using the same method as Zhao, Ma et al confirmed the results of Zhao and also found that large V values favor polaron transport while small values of V suppress the polaronic motion [18].…”

“…In Ref. [18], Ma et al discussed polaron dynamics using the extended Hubbard model, taking only the nearest-neighbor e-e interactions into consideration. They found that the saturated velocity of the polaron decreased monotonically with increasing nearest-neighbor interactions except for the cases U < 0:25 eV, which are shown in Fig.…”