Kagome Films on Demand

A new process, coined kagomerization, leads to one-atomic-thick films forming truly 2D kagome lattices

18 July 2024

Kagome is a traditional Japanese woven bamboo pattern. Intriguingly, quantum materials can also form Kagome structures. The kagome lattice, a two-dimensional network of corner-sharing triangles, offers a vibrant platform for the emergence of nontrivial quantum states driven by electronic correlations such as unconventional superconductivity, charge and spin density waves, and unusual magnetic states such as quantum spin liquids.

Schematic representation of the heavy-metal (HM) substrate with an epitaxial 3d transition metal (TM) monolayer, capped by two-dimensional hexagonal boron nitride. Copyright: Zhou, H., dos Santos Dias, M., Zhang, Y. et al., Nat. Commun. 2024, DOI: https://doi.org/10.1038/s41467-024-48973-z, CC BY 4.0

However, while kagome lattices have a pure 2D geometry, it has so far only been possible to realize them in 3D as complex multi-atomic bulk compounds, which makes the connection to the physics of 2D kagome lattices less transparent. In search of a 2D Kagome material, researchers at Forschungszentrum Jülich, together with Chinese partners, have now introduced a new process that leads to a one-atomic-thick film forming a truly 2D kagome lattice.

Scientific results

In their work published in the scientific journal Nature Communications, the researchers describe a novel fabrication process, that they coined “kagomerization” as demonstrated by high throughput simulations. The process leads to a structural rearrangement of one-atomic-thick transition metal films in order to form a kagome lattice. This is made possible by the wise combination of interfaces. The monolayers are covered with the 2D material hexagonal boron nitride. The fabrication process is found universal for transition metal films grown on heavy metal surfaces. These materials are also used as building-block materials in spintronics, where the magnetic moment of the electron is to be harnessed for information processing.

The surprising finding is that the hexagonal boron nitride layer seems to play an essential role in facilitating the kagomerization process, as the researchers could show. Previously it was considered a passive layer in the quantum materials community. The newly found Kagome structures exhibit rich electronic and magnetic properties and can host topological magnetic knots such as skyrmions and merons. These unique particles hold significant promise as magnetic bits for the next generation of information storage and processing devices.

The new findings offer wide and new perspectives in the realization and the exploration of the highly-sought kagome lattices and the underlying intertwining of topology, electron-correlations and magnetism. The profound impact on magnetic properties, coupled with the observed tunability through magnetic fields, opens up promising avenues in the realm of information technology. The researchers anticipate the potential to engineer material coverage, with and without hexagonal boron nitride, through techniques such as lithography. These distinct material areas hold the promise of harboring diverse topological states, which can be tailored to serve as fundamental components in spintronic circuitry.

Reshaping of the TM layer from an hexagonal to a kagome lattice induced by two-dimensional hexagonal boron nitride. Copyright: Zhou, H., dos Santos Dias, M., Zhang, Y. et al., Nat. Commun. 2024, DOI: https://doi.org/10.1038/s41467-024-48973-z, CC BY 4.0

Original publication

Zhou, H., dos Santos Dias, M., Zhang, Y. et al.
Kagomerization of transition metal monolayers induced by two-dimensional hexagonal boron nitride.
Nat Commun (2024), DOI: 10.1038/s41467-024-48973-z