Phase-dependent exciton transport and energy harvesting from thermal environments

TL;DR

This paper reveals how phase relations in initial states can cause ultrafast, non-Markovian energy relaxation in quantum systems, leading to transient uphill energy flow from the environment, with implications for quantum energy harvesting.

Contribution

It uncovers a phase-dependent environmental process causing energy relaxation and uphill energy flow, highlighting non-secular effects in non-Markovian quantum dynamics.

Findings

Energy relaxation depends on initial phase relations.

Transient uphill energy flow violates detailed balance.

Non-secular environmental contributions are key.

Abstract

Non-Markovian effects in the evolution of open quantum systems have recently attracted widespread interest, particularly in the context of assessing the efficiency of energy and charge transfer in nanoscale biomolecular networks and quantum technologies. With the aid of many-body simulation methods, we uncover and analyse an ultrafast environmental process that causes energy relaxation in the reduced system to depend explicitly on the phase relation of the initial state preparation. Remarkably, for particular phases and system parameters, the net energy flow is uphill, transiently violating the principle of detailed balance, and implying that energy is spontaneously taken up from the environment. A theoretical analysis reveals that non-secular contributions, significant only within the environmental correlation time, underlie this effect. This suggests that environmental energy harvesting will be observable across a wide range of coupled quantum systems.