This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: How atoms are arranged inside materials can influence the behavior of electrons and the resulting electronic states. Kagome lattices, repeating arrangements of atoms forming triangles that share corners (with hexagonal spaces between them), have been linked with the emergence of unusual electronic states.
Researchers at Seoul National University, the Center for Complex Phase of Materials and other institutions recently realized a two-dimensional (2D) kagome material that could be used to investigate quantum physics phenomena. This material, presented in a paper published in Nature Physics, was found to retain a set of tunable electron states with nearly identical energies (i.e., a flat electronic band) in a single layer. "A central theme in condensed matter physics is the emergence of new electronic behavior from the underlying lattice geometry and symmetry," Mingu Kang, senior author of the paper, told Phys.org.
"A well-known example is graphene, where the symmetry of its hexagonal lattice gives rise to massless Dirac electrons (m = 0). Another extensively studied example in theoretical physics is the kagome lattice, composed of corner-sharing triangles." Kagome lattices get their name from a traditional Japanese basket-weaving pattern. In kagome materials, atoms are arranged in a similar pattern, which can give rise to unusual electronic and magnetic behavior.
"As opposed to a hexagonal lattice, the kagome lattice can host flat band electrons, which behave as if they have an extremely large effective mass (m = ∞)," explained Kang. "Such flat bands provide a promising setting for discovering exotic quantum phenomena, including unconventional superconductivity and fractional quantum states. However, most existing kagome materials are three-dimensional, where interactions between layers and other complexities obscure the underlying kagome physics." Kang and his colleagues wanted to experimentally realize an ideal single-layer kagome system with an isolated flat electron band, which they called kagomene.
They then planned to examine this material to confirm whether it hosted flat band electrons, electrons that occupy states in which their energy changes very little with momentum. Flat band electrons can drive some quantum phenomena. Materials with a flat electronic band could thus be used to observe and explore these phenomena.
"The most important breakthrough of our research was the identification of a new van der Waals (vdW) kagome material, A2T3X4, which allows us to realize a single-layer kagome lattice through standard mechanical exfoliation," said Kang. "To this end, we identified a suitable vdW kagome material through a systematic, high-throughput screening process." Kang and his colleagues created a database that contains approximately 183,000 materials, roughly 5,300 of which were found to contain kagome lattice structures. The researchers then examined these kagome materials and identified those with neighboring layers held together by relatively weak forces that could make them easier to peel apart into thinner sheets.
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