Professor Emi Minamitani, SANKEN

Where physics meets topology: a research journey into the structure of amorphous materials

Even something as ordinary as window glass hides a surprisingly complex atomic structure. Although it appears transparent and uniform, the atoms inside glass are arranged irregularly. A new study by Professor Emi Minamitani’s research team, published in Nature Communications, reveals how this hidden structure influences the way amorphous materials respond to mechanical stress [1]. By applying a mathematical method known as persistent homology, the researchers uncovered structural patterns that help explain the mechanical behavior of these materials.

“It took six rounds of back-and-forth with the reviewers before publication,” she says with a smile. “The publication process took about a year and required considerable persistence.”

Topological data analysis reveals hidden structures in amorphous materials

In this study, Professor Minamitani’s team applied persistent homology, a method from topological data analysis, to investigate the atomic structure of amorphous materials in a new way. The technique allows researchers to detect ring-like atomic structures of different sizes formed by atoms within the material. These rings reflect the medium-range order hidden in amorphous structures, allowing the team to examine how atomic arrangements relate to non-affine deformation, a characteristic mechanical response of amorphous materials.

The analysis revealed that regions prone to non-affine deformation possess a distinctive nested hierarchical structure in which order and disorder coexist. In particular, the researchers found that small rings with irregular edge lengths are embedded within larger rings, forming layered structural patterns.

This discovery provides a new perspective on how atomic arrangements influence the mechanical behavior of amorphous materials. By identifying structural features associated with deformation, the findings may help guide the development of shatter-resistant glass and flexible, durable amorphous materials in the future.

Fig. 1 Summary of the present study: Persistence diagram obtained from the structure of amorphous silicon, examples of the local ring structures corresponding to each point in the diagram, and representative structures including atoms with large nonaffine displacements.

(License)Original content (Usage restriction) Credit must be given to the creator. (Credit) Emi Minamitan

How did the idea emerge?

She has always valued spending time learning about fields beyond her primary research area.

Professor Minamitani’s research background is in solid-state physics. During the COVID-19 pandemic, when she was forced to work from home, she began studying topology, a branch of mathematics she had long been curious about. At the time, she did not yet have a clear idea of how it might connect to her own research.

Over time, however, several experiences gradually led her toward the present study.

One of these turning points came from a personal memory. As a child, Professor Minamitani loved glassware. She enjoyed collecting small, delicate glass objects, but they would sometimes break. Each time, she remembers feeling deeply disappointed.

Those experiences left her with a lasting fascination with glass. However, because her academic career developed in a completely different field, she never initially imagined that glass would one day become connected to her research.

Meanwhile, through interactions with other researchers, she also became acquainted with scientists studying amorphous materials, including glass. This became another important turning point.

Through these encounters, she gained insight into current research trends in the field of amorphous materials and began to see how mathematical tools such as topology might be applied to these complex systems.

Curiosity and encounters shaping new discoveries

Looking back, Professor Minamitani reflects that research ideas often emerge in unexpected ways. Even if a new idea or field of study does not seem immediately useful, experiences accumulated over time—through learning, conversations, and chance encounters—can eventually come together and lead to new discoveries.

She is currently exploring collaborative research projects related to persistent homology with researchers at Seoul National University and the University of Oxford. Driven by her wide-ranging curiosity and collaborations with researchers across disciplines, it will be exciting to see where her research leads next.

[1] Emi Minamitani, Takenobu Nakamura, Ippei Obayashi, Hideyuki Mizuno, “Persistent homology elucidates hierarchical structures responsible for mechanical properties in covalent amorphous solids”, Nature Communications, 2025, 16, Article number: 8226, https://doi.org/10.1038/s41467-025-63424-z

For further information: https://www.sanken.osaka-u.ac.jp/labs/cmp/en/