Abstract
The time-dependent wavepacket diffusion method for carrier quantum dynamics (Zhong and Zhao 2013 J. Chem. Phys. 138 014111), a truncated version of the stochastic Schrödinger equation/wavefunction approach that approximately satisfies the detailed balance principle and scales well with the size of the system, is applied to investigate the carrier transport in one-dimensional systems including both the static and dynamic disorders on site energies. The predicted diffusion coefficients with respect to temperature successfully bridge from band-like to hopping-type transport. As demonstrated in paper I (Moix et al 2013 New J. Phys. 15 085010), the static disorder tends to localize the carrier, whereas the dynamic disorder induces carrier dynamics. For the weak dynamic disorder, the diffusion coefficients are temperature-independent (band-like property) at low temperatures, which is consistent with the prediction from the Redfield equation, and a linear dependence of the coefficient on temperature (hopping-type property) only appears at high temperatures. In the intermediate regime of dynamic disorder, the transition from band-like to hopping-type transport can be easily observed at relatively low temperatures as the static disorder increases. When the dynamic disorder becomes strong, the carrier motion can follow the hopping-type mechanism even without static disorder. Furthermore, it is found that the memory time of dynamic disorder is an important factor in controlling the transition from the band-like to hopping-type motions.
Highlights
IntroductionCoherent quantum transport of energy and charge has attracted much interest because of the fundamental scientific values as well as technological implications of artificial light-harvesting systems, organic photovoltaics, DNA, etc [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]
In order to clarify the effects of these disorders on carrier dynamics, three regimes from the weak, intermediate and strong dynamic disorder strengths are analyzed in the present paper
At the weak dynamic disorder, the carrier diffusion coefficient is nearly independent of temperature at low temperatures, and linearly increases with temperature (D ∝ T ); it becomes proportional to 1/ T at very high temperatures, which can be roughly predicted from the classical Marcus formula
Summary
Coherent quantum transport of energy and charge has attracted much interest because of the fundamental scientific values as well as technological implications of artificial light-harvesting systems, organic photovoltaics, DNA, etc [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]. For homogeneous systems with strong dynamic disorder, the transport is assumed to follow the hopping mechanism where the carrier hops incoherently between adjacent molecular sites [27] In this case, Fermis golden rule (FGR) (small polaron theory) [21, 28] was originally proposed to describe the hopping rate in organic crystals, and the well-known Marcus formula [29, 30] corresponds to its high-temperature limit. Several analytic expressions and numerical simulations [31,32,33,34,35,36,37] have revealed that while any finite amount of static disorder leads to a lack of diffusion in one- or two-dimensional systems, adding a dynamic disorder can be sufficient to allow for transport to occur by destroying the phase coherence responsible for Anderson localization.
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