Dr. Farinacci and her colleagues from the Freie University Berlin have realized a magnetic kagome lattice on a superconductor using molecular self-assembly of Fe-porphin-chloride molecules on Pb(111).
Kagome lattices were already part of our ancestors' daily lives, as they are a traditional weaving pattern in Japan used particularly to shape light and sturdy baskets. Remarkably, this design, made of corner-sharing triangles, may very well be a fundamental constituent of future technologies, as the properties of their band structures cast kagome materials as versatile platforms to explore a wide variety of fascinating phenomena. The presence of a flat band makes them prone to many-body correlations, and Dirac cones allow for the study of relativistic effects. Additionally, the geometry of the lattice frustrates spin interactions, and spin-orbit interaction can lead to the opening of a topological gap.
So far, most studies of kagome lattices have relied on three-dimensional materials with stacks of kagome lattices. Inter-layer coupling may influence the properties of the band structure and attenuate the effects of topology and correlations. Here, the researchers circumvented this issue by realizing a purely two-dimensional kagome lattice using molecular self-assembly. Another challenge was to minimize the influence of the substrate, as hybridization with a metallic bath would also affect the lattice properties. The innovative approach of the team was to use magnetic bound states inside a superconductor to study the lattice formation, as these are protected by the superconducting gap.
By depositing Fe-porphin-chloride molecules on Pb(111) and tuning the sample temperature during and after molecular deposition, the researchers were able to control the formation of small-range kagome precursors and long-range kagome islands. This allowed them to study the hybridization of the magnetic bound states from precursors, in which a few sites are coupled together with energetically separated hybridized states, to large domains in which bands are formed within the kagome lattice. This novel approach is particularly promising for future studies of spin-liquid or Kondo-lattice behaviors in 2D platforms.
Original publication
- Farinacci, G. Reecht, F. von Oppen, K.J. Franke. Yu-Shiba-Rusinov bands in a self-assembled kagome lattice of magnetic molecules. Nature Communications 15, 6474 (2024)
Contact
Dr. Laëtitia Farinacci, laetitia.farinacci@fmq.uni-stuttgart.de