In a groundbreaking advancement at the intersection of optics and condensed matter physics, researchers from the University of Stuttgart’s Fourth Physics Institute have unveiled a remarkable phenomenon: "skyrmion bags" of light generated on the surface of a metal layer. This breakthrough opens an exciting new frontier in manipulating light in ways that defy conventional optical limitations, potentially paving the way for revolutionary improvements in microscopy and photonics technologies.
Skyrmions, originally conceived in nuclear physics, are topologically protected vortex-like configurations that have captivated scientists across various disciplines. These intricate structures, representing localized twists in a field, have been validated experimentally in magnetic materials and other complex matter phases over the past decade. The Stuttgart team has now succeeded in extending this concept to the manipulation of light fields, demonstrating that structured light interacting with precisely engineered metal surfaces can form stable skyrmion configurations conserved within larger skyrmion “bags.”
Central to this achievement was the fabrication of nanoscale patterns etched into a thin gold film with unprecedented precision. The team sculpted two intertwined hexagonal arrays of fine grooves onto the metal surface, each acting as a source for generating distinct skyrmion light fields. By controlling the moiré superlattice—interference patterns arising from the overlay of these twisted hexagonal lattices—the researchers could dictate the spatial arrangement and topological properties of the resulting plasmonic fields.
The experimental observations, led by doctoral researcher Julian Schwab, revealed that when two such skyrmion light fields merged, they gave rise to complex skyrmion bag states. These hierarchical structures consist of multiple skyrmions nested within a larger encompassing skyrmion, a configuration that until now existed primarily in theoretical constructs. Through careful tuning of the relative twist angle between the moiré lattices, Schwab and colleagues achieved deterministic control over the number and arrangement of individual skyrmions within each bag, effectively “sculpting” light fields with new symmetries and topologies.
This exquisite manipulation of plasmonic waves is far more than a scientific curiosity; it challenges prevailing boundaries in optical physics by generating light structures that do not naturally occur in free space. The potential applications of such controlled light topology are vast. For instance, the ability to engineer skyrmion bags could drastically enhance resolution beyond the diffraction limit in optical microscopy, enabling scientists to visualize nanoscopic details of biological and material samples with unmatched clarity.
Moreover, plasmons—collective oscillations of electrons coupled with photons—play a crucial role in this research. The structured gold surface supports surface plasmon polaritons, which confine light to scales far below its wavelength. By exploiting the unique interplay between plasmonic excitation and topological field configurations, the team effectively bridges the gap between light’s wave nature and particle-like topological robustness, offering new platforms to explore ultrafast nano-optics and information processing.
The implications of these findings reach into fundamental physics as well. Skyrmions, due to their topological protection, are immune to certain perturbations and defects, making them promising candidates for stable information carriers. By translating skyrmion physics into the optical domain, researchers may one day realize robust optical storage or logic devices that utilize the twisted nature of light, pushing quantum technologies closer to realization.
This endeavor was a highly interdisciplinary collaboration spanning institutions and expertise. Besides the University of Stuttgart’s experimental efforts, theoretical insights were contributed by the Technion in Haifa, which helped model and predict the behavior of these plasmonic skyrmion bags. Additionally, the University of Duisburg-Essen partnered in verifying the experimental conditions, ensuring the reproducibility and precision of the nanoscale patterning techniques employed.
While the current experiments harness gold as the plasmonic substrate, questions remain about the optimal materials to maximize the stability and efficiency of skyrmion light fields. Harald Giessen, head of the research group, envisions that future work will explore alternative plasmonic metals and novel two-dimensional materials to finetune these effects. Such advancements are critical for translating this fundamental physics insight into practical technologies.
On the theoretical front, this research deepens our understanding of moiré superlattices, a topic of intense study due to its relevance in exotic quantum phases such as superconductivity and correlated insulators. The plasmonic moiré lattices fashioned here represent an optical analog to these electronic systems, revealing new possibilities to control light-matter interactions through engineered symmetry-breaking and topological order.
Furthermore, the exquisite tunability demonstrated—varying the twist angle to adjust the skyrmion count within each bag—echoes themes emerging in the study of twisted bilayer graphene and other van der Waals heterostructures. It underscores a broader trend in physics: topology and moiré engineering as universal tools to unlock new states of matter and light.
The timing of this breakthrough could not be more exciting. As ultrafast laser technologies and nanoscale fabrication techniques continue to evolve, the capacity to create and manipulate complex light fields at will offers a new playground for experimentalists and theorists alike. The Fourth Physics Institute’s leadership in this domain solidifies their position at the forefront of ultrafast nano-optics research.
With the potential to overcome diffraction limits and create robust optical structures immune to disturbances, skyrmion bags of light may soon find applications not only in sophisticated microscopy but also in optical communication, quantum computing, and sensing technologies. While still in the early stages, this discovery heralds a shift towards topologically engineered photonics, enriching the toolkit scientists have to control light-matter interactions on the smallest scales.
In summary, the creation and control of skyrmion bags of light in plasmonic moiré superlattices represents a monumental stride forward in our ability to tailor complex light fields. By synergizing concepts from topology, plasmonics, and moiré physics, the team at the University of Stuttgart has opened promising avenues for both basic science and transformative technological applications. This fusion of theoretical elegance and experimental precision marks a milestone in the quest to harness light’s full potential in unprecedented ways.
Subject of Research:
Ultrafast nano-optics, plasmonic moiré superlattices, topological light fields
Article Title:
Skyrmion bags of light in plasmonic moiré superlattices
News Publication Date:
22-Apr-2025
Web References:
https://dx.doi.org/10.1038/s41567-025-02873-1
https://www.uni-stuttgart.de/universitaet/aktuelles/meldungen/Physiker-entdecken-versteckte-Symmetrie-exotischer-Kristalle/
References:
Julian Schwab, Alexander Neuhaus, Pascal Dreher, Shai Tsesses, Kobi Cohen, Florian Mangold, Anant Mantha, Bettina Frank, Guy Bartal, Frank-J. Meyer zu Heringdorf, Timothy J. Davis & Harald Giessen: Skyrmion bags of light in plasmonic moiré superlattices. Nature Physics, DOI: 10.1038/s41567-025-02873-1.
Image Credits:
University of Stuttgart / 4th Physics Institute
Keywords
Skyrmions, plasmonics, topological photonics, moiré superlattices, ultrafast nano-optics, gold nano-patterning, light field manipulation, diffraction limit, surface plasmon polaritons, nanoscale optics, optical microscopy, topological light structures
