On the role of non-diagonal system–environment interactions in bridge-mediated electron transfer

Abstract

Bridge-mediated electron transfer (ET) between a donor and an acceptor is prototypical for the description of numerous most important ET scenarios. While multi-step ET and the interplay of sequential and direct superexchange transfer pathways in the donor-bridge-acceptor (D-B-A) model is increasingly understood, the influence off-diagonal system-bath interactions on the transfer dynamics is less explored. Offdiagonal interactions account for the dependence of the ET coupling elements on nuclear coordinates (non-Condon effects) and are typically neglected. Here we numerically investigate with quasi-adiabatic propagator path integral (QUAPI) simulations the impact of off-diagonal system-environment interactions on the transfer dynamics for a wide range of scenarios in the D-B-A model. We demonstrate that off-diagonal system-environment interactions can have profound impact on the bridge-mediated ET dynamics. In the considered scenarios the dynamics itself does not allow for a rigorous assignment of the underlying transfer mechanism. Further, we demonstrate how off-diagonal system-environment interaction mediates anomalous localization by preventing long-time depopulation of the bridge B and how coherent transfer dynamics between donor D and acceptor A can be facilitated. The arising non-exponential short-time dynamics and coherent oscillations are interpreted within an equivalent Hamiltonian representation of a primary reaction coordinate model that reveals how the complex vibronic interplay of vibrational and electronic degrees of freedom underlying the non-Condon effects can impose donor-to-acceptor coherence transfer on short timescales.

Excitons: Energetics and spatio-temporal dynamics

“…Mixed quantum-classical nonadiabatic quantum dynamics approaches based on the QCLE are addressed by Kim and Rhee; 37 these can potentially be generalized for a large class of molecular systems but rely on certain kinds of approximations that become reasonable in the semiclassical or classical limits of nuclear degrees of freedom. Finally, Acharyya et al 38 report application of a path integral approach for donor-bridge-acceptor (DBA) model with off-diagonal couplings. Although this work more specifically addresses electron transfer process, the observed results are equally effective in DBA exciton transfer system.…”

Non-Markovian temperature sensing

“…In Refs. [49][50][51][52], sin θσ z is named as the diagonal coupling term, while cos θσ x is called the off-diagonal coupling operator. However, such a naming convention may lead to misunderstanding when the diagonal and the off-diagonal terms are included in both Ĥs and Ŝ at the same time.…”

Quantum Thermal Transport Beyond Second Order with the Reaction Coordinate Mapping

“…The spin-boson model has been recently extended to explore dynamics and transport effects using a general coupling operator with both diagonal and off-diagonal couplings 18,[49][50][51][52][53][54][55][56][57][58][59] . For heat transport, the coupling operators to the different reservoirs do not commute.…”