Influence of Coherent Tunneling and Incoherent Hopping on the Charge Transfer Mechanism in Linear Donor–Bridge–Acceptor Systems

Abstract

The mechanism of charge transfer has been observed to change from tunneling to hopping with increasing numbers of DNA base pairs in polynucleotides and with the length of molecular wires. The aim of this paper is to investigate this transition by examining the population dynamics using a tight-binding Hamiltonian with model parameters to describe a linear donor-bridge-acceptor (D-B-A) system. The model includes a primary vibration and an electron-vibration coupling at each site. A further coupling of the primary vibration with a secondary phonon bath allows the system to dissipate energy to the environment and reach a steady state. We apply the quantum master equation (QME) approach, based on second-order perturbation theory in a quantum dissipative system, to examine the dynamical processes involved in charge-transfer and follow the population transfer rate at the acceptor, ka, to shed light on the transition from tunneling to hopping. With a small tunneling parameter, V, the on-site population tends to localize and form polarons, and the hopping mechanism dominates the transfer process. With increasing V, the population tends to be delocalized and the tunneling mechanism dominates. The competition between incoherent hopping and coherent tunneling governs the mechanism of charge transfer. By varying V and the total number of sites, we also examine the onset of the transition from tunneling to hopping with increasing length.

Dramatic changes in DNA conductance with stretching: structural polymorphism at a critical extension

“…Since the DNA we have studied is short in length (12 bp), the transport of charge will have also a contribution from tunneling. 50,51 However the main conclusions (critical stretching length) of the paper remain and do not change due to the inclusion of tunneling (see section X of the ESI †). The stretching length vs. current calculation described above was performed at 300 K. To understand the effect of temperature on the dynamics we also calculated the response for 5′end1-5′end2 pulling at 350 K and 250 K. The H-bond profiles are shown in Fig.…”

Challenges in engineering conductive protein fibres: Disentangling the knowledge

“…[6,29] This switchover of mechanism has been observed on other organic molecules such as donorbridge-acceptor systems or DNA, where electron tunnelling gives way to multi-step hopping as the distance the electron must travel increases. [117][118][119][120][121][122] In addition, spacing differences in interdigitated electrode arrays have been shown to change how quickly steady-state current is reached in electrochemical experiments. [123] Even electrode area has been reported to change current-voltage responses in G. sulfurreducens biofilms.…”

Trapping and transport of charges in DNA by mobile discrete breathers

“…Изучаются детали механизмов взаимодействия электронов с возмущениями цепочки нуклеотидов [23][24][25], рассчитываются вольт-амперные характеристики молекулы ДНК [26,27], анализируются способы управления характеристиками транспорта зарядов [28,29], исследуется влияние внешней среды [30], рассматриваются как перспективные сложные модификации, включающие ДНК [31][32][33][34][35][36], описываются различные прикладные возможности [37].…”