Topologically-enhanced exciton transport

TL;DR

This paper demonstrates that topological properties of excitons can significantly enhance their diffusion in various regimes, offering new avenues for improving optoelectronic device efficiency through quantum geometric concepts.

Contribution

It introduces a general theory linking topological excitons to enhanced diffusion and applies it to organic semiconductors, also proposing experimental probes of quantum geometry.

Findings

Topological excitons are larger and more dispersive than trivial ones.

Exciton transport can increase up to fourfold with topological effects.

Electric fields can probe the quantum metric of excitons.

Abstract

Excitons dominate the optoelectronic response of many materials. Depending on the time scale and host material, excitons can exhibit free diffusion, phonon-limited diffusion, or polaronic diffusion, and exciton transport often limits the efficiency of optoelectronic devices such as solar cells or photodetectors. We demonstrate that topological excitons exhibit enhanced diffusion in all transport regimes. Using quantum geometry, we find that topological excitons are generically larger and more dispersive than their trivial counterparts, promoting their diffusion. We apply this general theory to organic polyacene semiconductors and show that exciton transport increases up to fourfold when topological excitons are present. We also propose that non-uniform electric fields can be used to directly probe the quantum metric of excitons, providing a rare experimental window into a basic geometric feature of quantum states. Our results provide a new strategy to enhance exciton transport in semiconductors and reveal that mathematical ideas of topology and quantum geometry can be important ingredients in the design of next-generation optoelectronic technologies.