A joint research team from NIMS, Toyota Kosen (National Institute of Technology, Toyota College), Saga University, Nara Women's University, Kiel University (Germany), and other institutions fabricated a two-dimensional structure that exhibits properties of both the honeycomb and Kagome lattices using organic molecules. They discovered that edge states specific to topological materials (states that exist only at the edges, which are distinct from those in the interior) appear in this structure. While organic molecules allow for the flexible design of structures, it is difficult to strongly bind the molecules together electronically. Therefore, inorganic materials had mainly been used to synthesize topological materials. The team's success in realizing unique electronic states in an assembly of organic molecules (a supramolecular structure) paves the way for a new quantum material design approach using organic molecules. This research result was published in Nano Letters on September 2, 2026.
Background
While quantum technology is an innovative technology that is expected to fundamentally transform society, its future advancement relies on the development of quantum materials, which serve as its foundation. However, most of the conventionally known quantum materials were composed of inorganic materials, and they had significant issues regarding flexibility in design and synthesis. On the other hand, supramolecular structures formed by the assembly of organic molecules have the characteristic of allowing for flexible design. Nevertheless, since supramolecules generally have weak electronic coupling between their constituent units, they were not suitable for use as quantum materials. Therefore, there had been a call for the development of a new design method for quantum materials based on organic molecules.
Key Findings
In this study, the research team succeeded in creating a two-dimensional structure that exhibits the properties of both the honeycomb and Kagome lattices (a diatomic Kagome lattice) by assembling an organic molecule derived from a triptycene molecule (a triptycene derivative; see Figure, left) as building blocks. The honeycomb lattice has a structure resembling bees' honeycomb, as the name suggests, which is found in graphene (a single layer of graphite), while the Kagome lattice has a structure resembling the lattice pattern of a traditional Japanese Kagome craft basket. Due to their unique electronic states, these lattices have been studied actively in recent years. However, hardly any studies have created a diatomic Kagome lattice, which can be described as a hybrid of these two lattices, in an actual material.
Further, when the research team observed the prepared sample using a scanning tunneling microscope, they discovered a unique electronic state that exists only in the boundary (edge) region between the two-dimensional structure of the organic molecules and its exterior. They conducted a detailed theoretical analysis, and found that this state is a topological edge state derived from its mathematical structure (technically called topology). This clearly demonstrates the properties of this sample as a quantum material. The reason that the structure exhibits such a state despite being composed of organic molecules is that the organic molecules are strongly bonded to each other. This stems from the fact that the three planes constituting the triptycene derivative are arranged in a three-dimensional propeller-like configuration, with adjacent planes in contact with one another (the coupling is denoted as t1 in Figure, right). The fact that the team was able to design and synthesize this unique molecular structure and to assemble the molecules into a supramolecular structure was the key to achieving this research result.
Future Outlook
Based on this result, we will accelerate the development of materials for the application of quantum technology. For example, by utilizing such unique lattice structure, it may become possible to switch between a high-mobility semiconductor-like state and a superconducting state, achieve ultra-high-speed, ultra-low-power optical switching, and even enable lossless energy transport at room temperature. We will also work to realize a variety of quantum materials by making use of organic molecules in that they enable flexible design.
Other Information
- This research was conducted by a team led by Takashi Uchihashi (Deputy Director, Research Center for Materials Nanoarchitectonics [MANA], NIMS), Ryuichi Arafune (Principal Researcher, MANA, NIMS), Katsunori Wakabayashi (Group Leader, MANA, NIMS), Kunio Awaga (President, Toyota Kosen), Rie Suizu (Associate Professor, Saga University), Masahisa Tsuchiizu (Associate Professor, Nara Women's University), and Richard Berndt (Professor, Kiel University, Germany), as part of JSPS Grants-in-Aid for Scientific Research (grant numbers: 25H00867, 25K01670, 20H05621, 20H02707, 23K03322, 25K01609, and 22H05473), Strategic Basic Research Program PRESTO (grant number: JPMJPR21A9), and the World Premier International Research Center Initiative (WPI), Ministry of Education, Culture, Sports, Science and Technology.
- This research result was published online in Nano Letters issued by the American Chemical Society on September 2, 2026.
