Coherent quantum transport in disordered systems I: The influence of dephasing on the transport properties and absorption spectra on one-dimensional systems

TL;DR

This paper investigates how dephasing influences excitonic transport and absorption spectra in disordered one-dimensional systems, revealing a maximum in diffusion rate and the conditions for enhanced quantum transport.

Contribution

It introduces quantum master equations for weak and strong dephasing regimes and demonstrates the existence of a maximum diffusion constant as a function of dephasing rate.

Findings

Transport transitions from non-diffusive to diffusive with increasing dephasing.

Diffusion constant peaks at an optimal dephasing rate.

Diffusion constant scales with the square of the localization length in weak dephasing.

Abstract

Excitonic transport in static disordered one dimensional systems is studied in the presence of thermal fluctuations that are described by the Haken-Strobl-Reineker model. For short times, non-diffusive behavior is observed that can be characterized as the free-particle dynamics in the Anderson localized system. Over longer time scales, the environment-induced dephasing is sufficient to overcome the Anderson localization caused by the disorder and allow for transport to occur which is always seen to be diffusive. In the limiting regimes of weak and strong dephasing quantum master equations are developed, and their respective scaling relations imply the existence of a maximum in the diffusion constant as a function of the dephasing rate that is confirmed numerically. In the weak dephasing regime, it is demonstrated that the diffusion constant is proportional to the square of the localization length which leads to a significant enhancement of the transport rate over the classical prediction. Finally, the influence of noise and disorder on the absorption spectrum is presented and its relationship to the transport properties is discussed.