Simple Chemical Rules for Predicting Band Structures of Kagome Materials

Abstract

Compounds featuring a kagome lattice are studied for a wide range of properties, from localized magnetism to massless and massive Dirac Fermions. These properties come from the symmetry of the kagome lattice, which gives rise to Dirac cones and flat bands. However, not all compounds with a kagome sublattice show properties related to it. We derive chemical rules predicting if the low-energy physics of a material is determined by the kagome sublattice and bands arising from it. After sorting out all known crystals with the kagome lattice into four groups, we use chemical heuristics and local symmetry to explain additional conditions that need to be met to have kagome bands near the Fermi level.

Crystal Net Catalog of Model Flat Band Materials

“…In the future, this flat band search method could be extended to produce additional flat band models and more accurate results by including these effects. More sophisticated search algorithms are also of significant interest; in particular, comparison with recent geometry-and DFT-based catalogs [45][46][47] may provide new insights for both theoretical models and identification of experimental materials targets.…”

A Tour of Soft Atomic Motions: Chemical Pressure Quadrupoles Across Transition Metal–Main Group 1:2 Structure Types

“…For intermetallic phasessolid state compounds composed of two or more metallic elementssuch relationships are still needed for diverse properties such as superconductivity, − permanent magnetism, − thermoelectricity, − and catalysis. , The gap between structure and properties in intermetallics is further widened by a vast range of possible elemental combinations coupled with the boundless variability of crystal structures they can adopt. Nevertheless, immense progress has been made in connecting intermetallics and their properties: the phonon–glass/electron–crystal model provides a guiding principle for the search for thermoelectric materials, − specific sublattice geometries are associated with unique band structures and physical behavior, − and packings of magnetically active elements in triangular arrangements are associated with complex phenomena arising from frustration. − …”

Oxygen-Terminated (1 × 1) Reconstruction of Reduced Magnetite Fe3O4(111)

“… 14 − 18 If the “biphase” termination does in fact contain a kagome layer with reduced coordination to oxygen, it may be interesting to investigate whether the weaker linking between iron atoms gives rise to clean kagome bands. 26 …”

“…The apparently flexible bond angles of the tetrahedrally coordinated iron in the kagome Fe oct1 layer could conceivably accommodate such an attachment. Of course, significant modifications of such structures and variations in stoichiometry may be necessary to explain the range of different morphologies observed for biphase structures. − If the “biphase” termination does in fact contain a kagome layer with reduced coordination to oxygen, it may be interesting to investigate whether the weaker linking between iron atoms gives rise to clean kagome bands …”