Excitons meet topology in organic materials

Researchers uncover topological excitons with enhanced transport properties, paving the way for next-generation optoelectronic devices.

“The Cavendish has a highly active research community seeking to understand and control excitons in a wide range of materials. We hope this new contribution will pave the way for many future interesting studies.”

Wojciech Jankowski

In 2016, three former members of the Cavendish Laboratory, Michael Kosterlitz, David Thouless, and Duncan Haldane received the Nobel Prize in physics for their groundbreaking work on topology in condensed matter. Their pioneering studies showed how the fundamental shape or “topology” of electronic wave functions manifests in unique properties, revolutionising a wide range of technologies from superconductors and sensors to quantum computers.

Carrying on this rich tradition, researchers from the Cavendish Laboratory have explored how topology manifests in more complex particles called excitons. Typically, excitons form when light is shone on a semiconductor, leading to Coulomb bound electron-hole pairs representing quantum packets of energy. The behaviour and evolution of these excitons dictate the properties and performance of a huge range of optoelectronic devices, such as solar cells and LEDs.

In two recent studies, both published in Nature Communications, a team of researchers from the Cavendish Laboratory and the Department of Materials Science and Metallurgy at the University of Cambridge, and from the University of Manchester demonstrated that topological excitons could be realised in organic semiconductors and that this inherent topology leads to a stark enhancement in their transport.

“We found a new class of excitonic particles with boosted mobility and exotic localisation in organic matter,” said Wojciech Jankowski, co-author of the study from Cambridge’s Cavendish Laboratory. “The Cavendish has a highly active research community seeking to understand and control excitons in a wide range of materials. We hope this new contribution will pave the way for many future interesting studies.”

Excitingly, the studies showed how the chemical tuning of organic semiconductors can be used to control this topology and enhance the transport of excitons. “The topology of excitons represents a whole new design paradigm for future devices” said Dr Joshua Thompson, co-author of the study from the Department of Materials Science and Metallurgy at Cambridge. “We show that excitons spread much faster, which is highly promising for a wide range of applications including more efficient solar cells.”

“Overall, we bring together two mature fields, topological condensed matter and the optoelectronics of organic semiconductors,” said Prof Robert-Jan Slager, co-author of the study from the University of Manchester and the Cavendish. “Merging previously distinct areas opens fresh research directions.”

In particular, topological excitons can be easily adjusted with experimental knobs such as strain and dielectric environment, making them useful for developing modern optoelectronic devices that can be finely controlled.

“The work links the fundamental physics of geometric phases and topological invariants to real materials and observables”, said Prof Bartomeu Monserrat, Professor of Materials Physics at Cambridge. “Moreover, these new topological excitons and their properties in organic polymers may be soon observed through state-of-the-art experiments performed in the Cavendish Laboratory. We believe that this will open up broad avenues for real-world applications, kickstarting a whole new field of research.”

References:

• Jankowski, W.J., Thompson, J.J.P., Monserrat, B. & Slager R.-J., ‘Excitonic topology and quantum geometry in organic semiconductors’, Nature Communications 16, 4661 (2025). DOI:10.1038/s41467-025-59257-5
• Thompson, J.J.P., Jankowski, W.J., Slager, R.-J., & Monserrat B., ‘Topologically enhanced exciton transport’, Nature Communications 16, 11448 (2025). DOI:10.1038/s41467-025-66276-9

Image:

Illustration of a topological exciton created by light and propagating along an organic polymer chain. Credit: Joshua J.P. Thompson