Coherent quantum dynamics in donor-bridge-acceptor systems: Beyond the hopping and super-exchange mechanisms

TL;DR

This paper introduces a polaron-transformed quantum master equation that unifies and extends existing theories of quantum transport, revealing new regimes of coherent energy transfer in donor-bridge-acceptor systems.

Contribution

It develops a novel PQME approach that interpolates between Redfield and Forster theories, capturing quantum coherence effects beyond traditional models.

Findings

PQME reduces to Redfield and Forster in their limits

Identifies new transport regimes in bridged systems

Shows minimal models for quantum coherent super-exchange

Abstract

The population transfer dynamics of model donor-bridge-acceptor systems is studied by comparing a recently developed polaron-transformed quantum master equation (PQME) with the well-known Redfield and Forster theories of quantum transport. We show that the PQME approach reduces to these two theories in their respective limits of validity and naturally interpolates between them as a function of the system-bath coupling strength. By exploring the parameter space of our model problem, we identify novel regimes of transport dynamics in bridged systems like those encountered in biological and organic energy transfer problems. Furthermore, we demonstrate that three-level systems like the ones studied herein represent ideal minimal models for the identification of quantum coherent transport as embodied in super-exchange phenomena that cannot be captured by Forster-like hopping approaches.