Japanese researchers built a rare “diatomic Kagome lattice” from propeller-shaped triptycene molecules and directly imaged an electronic state confined to its edges, a hallmark of topological matter.

Quantum materials, in which the strange rules of quantum mechanics produce unusual electronic behavior on a large scale, are almost always made of inorganic substances: metals, oxides, crystals grown at high temperatures. Organic molecules, the carbon-based building blocks of plastics and living things, are far easier to design and modify, but they usually interact too weakly with one another to produce such effects.

A team at Japan’s National Institute for Materials Science (NIMS) and collaborating institutions now reports an exception. In a study published in Nano Letters, the researchers describe a two-dimensional structure assembled from organic molecules that hosts a topological edge state, an electronic signature of a quantum material, and they observed it directly.

Honeycomb meets Kagome

The structure is built from a molecule derived from triptycene, an organic compound shaped like a three-bladed propeller. When the molecules assemble on a surface, they form a pattern that combines features of two famous lattices.

One is the honeycomb lattice, the hexagonal arrangement of carbon atoms in graphene. The other is the Kagome lattice, named after a traditional Japanese basket-weaving pattern of interlaced triangles surrounding hexagonal openings. Kagome lattices have attracted intense interest from physicists because their geometry can give rise to exotic electronic states, including flat energy bands in which electrons behave in highly correlated ways.

The combined pattern is called a diatomic Kagome lattice, and according to the researchers it had rarely been realized in an actual material.

In a simple Kagome lattice, each lattice site is occupied by a single unit. In a diatomic version, two distinct sites share the repeating pattern, adding complexity to how electrons can move. Theorists have predicted that such lattices can host flat bands, Dirac cones like those in graphene and topological states, but realizing them in real materials has proven difficult.

Propellers that touch

The key to the structure’s behavior is the shape of the molecule. Each triptycene unit has three flat planes arranged like the blades of a propeller. In the assembled lattice, the planes of neighboring molecules come into contact. That contact allows electrons to hop strongly between molecules, a property the researchers denote t1.

Weak electronic coupling has long been a limitation for organic materials. In most molecular crystals and assemblies, electrons are largely confined to individual molecules, and their ability to move between molecules is limited. By arranging the molecules so that their flat faces touch, the triptycene design overcomes that barrier.

Seeing the edge

The team examined the structure using scanning tunneling microscopy, a technique that brings an extremely sharp metal tip within a few atoms’ distance of a surface. By measuring the tiny electrical current that tunnels between the tip and the sample, the microscope can map both the arrangement of molecules and the distribution of electronic states.

The measurements revealed an electronic state confined to the boundary between the molecular structure and its surroundings. Theoretical analysis identified it as a topological edge state, specifically one associated with the zigzag edges of the lattice, as the paper’s title indicates.

Topological materials are defined by properties of their electronic structure that are robust against small disturbances, much as a doughnut keeps its hole however it is squeezed or stretched. A common consequence is that the interior of a material may behave one way, while special electronic states appear at its edges or surfaces. Observing such an edge state is strong evidence that the material has a topological character.

The 2016 Nobel Prize in Physics recognized theoretical work on topological phases of matter, and since then researchers have identified many inorganic topological materials. Building them from organic molecules has been more challenging.

Why organic quantum materials matter

Organic supramolecules, large assemblies of molecules held together by non-covalent interactions, offer enormous flexibility. Chemists can modify a molecule’s shape, size and chemical groups to tune how it assembles and how its electrons behave. If those materials can host quantum states, the result could be a highly designable family of quantum materials.

The researchers mention several possibilities that such materials might eventually offer, including switching between semiconductor-like and superconducting states, ultrafast and low-power optical switching, and lossless energy transport at room temperature. These are long-term prospects rather than demonstrated results. The current study establishes that organic assemblies can host topological electronic states, a first step toward exploring such applications.

A collaborative effort

The research team was led by Takashi Uchihashi, deputy director of the Research Center for Materials Nanoarchitectonics (MANA) at NIMS, and included Ryuichi Arafune, a principal researcher at MANA, and Katsunori Wakabayashi, a group leader at MANA. Collaborators included Kunio Awaga, president of Toyota Kosen; Rie Suizu, an associate professor at Saga University; Masahisa Tsuchiizu, an associate professor at Nara Women’s University; and Richard Berndt, a professor at Kiel University in Germany.

The project brought together expertise in molecular design, surface science and theoretical physics, reflecting the combination of skills needed to build and understand such materials. Designing the molecule required synthetic chemistry; assembling it into a well-ordered lattice and imaging its electronic states required advanced surface techniques; and confirming the topological nature of the observed state required theoretical modeling.

Future work will need to determine how robust the edge states are, how they depend on the molecule’s design and how the lattice behaves on different surfaces. If organic assemblies can reliably host topological states, chemists may gain a new set of tools for building quantum materials molecule by molecule.

The research was supported by JSPS Grants-in-Aid for Scientific Research, the JST PRESTO program and the World Premier International Research Center Initiative of Japan’s Ministry of Education, Culture, Sports, Science and Technology.

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Notes

1. “Direct Observation of the Zigzag Edge States of a Supramolecular Diatomic Kagome Lattice.” Nano Letters, 2026. DOI: 10.1021/acs.nanolett.6c03195.
2. National Institute for Materials Science. “Building quantum materials using supramolecular technology.” EurekAlert!, 22 October 2026. https://www.eurekalert.org/news-releases/1148803.