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Universal structure of exceptional points revealed in nonlinear light‑based systems
Exceptional points, or EPs for short, are among the phenomena of modern physics. These are special points or locations at which the properties of matter, space or time change. In a new theoretical study, researchers from the Institute for Photonic Quantum Systems (PhoQS) at Paderborn University, in collaboration with researchers from the University of Arizona, have shown that exceptional points in nonlinear systems follow a universal geometric order—something that was previously unclear. Their findings have been published in the journal Nature Communications.
Exceptional points are points in physical systems at which not only two eigenvalues but also the corresponding states merge. Such phenomena occur in so-called non-Hermitian systems, which are characterized, for example, by amplification, loss or interactions with their environment. They are the subject of intensive research in fields including optics, lasers, quantum systems and polariton condensates.
Until now, EPs have mainly been studied in linear systems. In such systems, they can often be described as isolated points in parameter space. However, many real physical systems are nonlinear: Their properties depend on the intensity, occupation or state of the system itself.
From isolated points to structure
"We were able to show that nonlinear exceptional points do not follow just any geometry," explains Dr. Stefan Schumacher, whose research group carried out the work. The theoretical study was led largely by Dr. Nai Kwong of the University of Arizona, as well as Jan Wingenbach in Schumacher's research group and Dr. Laura Ares in the research group of Dr. Jan Sperling, also of Paderborn University.
Close collaboration with Dr. Rolf Binder and Kwong of the University of Arizona was essential to the success of the work. Commenting on the findings, Wingenbach says, "The discovery of a universal cone-and-cusp structure came as a surprise. It shows that we can now understand the physics of nonlinear exceptional points much better. This is a crucial step toward making targeted use of these phenomena for future applications, for example, in sensor technology or functional photonic systems."
Schumacher adds, "Very different physical systems can exhibit the same characteristic structure in the vicinity of an exceptional point. This universal topology provides a kind of roadmap for identifying such points more precisely in the future, understanding them and making them usable for applications."
A roadmap for sensitive devices
The study offers a new perspective on known linear EPs and demonstrates how they are embedded in nonlinear systems. Exceptional points are considered promising for highly sensitive sensors because systems in their vicinity can react particularly strongly to small disturbances. At the same time, with nonlinear systems, it is crucial to understand what amplification is achievable and where the fundamental limits lie.
The new topological description can help determine such limits mathematically with precision and design robust, highly sensitive components for various physical platforms. In the long term, the work points to a deeper unity within nonlinear, non-Hermitian physics: Different systems can exhibit the same universal topological signature despite differing microscopic details.
Publication details
Nai-Hang Kwong et al, Universal topology of exceptional points in nonlinear non-Hermitian systems, Nature Communications (2026). DOI: 10.1038/s41467-026-72854-2
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Citation: Universal structure of exceptional points revealed in nonlinear light‑based systems (2026, July 23) retrieved 23 July 2026 from https://phys.org/news/2026-07-universal-exceptional-revealed-nonlinear-lightbased.html
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