In solid-state physics, the kagome metal or kagome magnet is a type of ferromagnetic quantum material. The atomic lattice in a kagome magnet has layered overlapping triangles and large hexagonal voids, akin to the kagome pattern in traditional Japanese basket-weaving. ^{[1] [2] [3] [4]} This geometry induces a flat electronic band structure with Dirac crossings, in which the low-energy electron dynamics correlate strongly. ^[5]

Electrons in a kagome metal experience a "three-dimensional cousin of the quantum Hall effect": magnetic effects require electrons to flow around the kagome triangles, akin to superconductivity. ^[5] This phenomenon occurs in many materials at low temperatures and high external field, but, unlike superconductivity, materials are known in which the effect remains under standard conditions. ^{[5] [6]}

The first room-temperature, vanishing-external-field kagome magnet discovered was the intermetallic Fe₃Sn₂, as shown in 2011. ^[7] Many others have since been found. Kagome magnets occur in a variety of crystal and magnetic structures, generally featuring a 3d- transition-metal kagome lattice with in-plane period ~5.5 Å. Examples include antiferromagnet Mn₃Sn, paramagnet CoSn, ferrimagnet TbMn₆Sn₆, hard ferromagnet (and Weyl semimetal) Co₃Sn₂S₂, and soft ferromagnet Fe₃Sn₂. Until 2019, all known kagome materials contained the heavy element tin, which has a strong spin–orbit coupling, but potential kagome materials under study (as of 2019 ^[update]) included magnetically doped Weyl-semimetal Co₂MnGa, ^[8] and the class AV₃Sb₅ (A = Cs, Rb, K). ^[9] Although most research on kagome magnets has been performed on Fe₃Sn₂, it has since been discovered that FeSn in fact exhibits a structure much closer to the ideal kagome lattice. ^[10]

A kagome lattice harbors massive Dirac fermions, Berry curvature, band gaps, and spin–orbit activity, all of which are conducive to the Hall Effect and zero-energy-loss electric currents. ^{[6] [11] [12]} These behaviors are promising for the development of technologies in quantum computing, spin superconductors, and low power electronics. ^{[5] [6]}  CsV₃Sb₅ in particular exhibits numerous exotic properties, including superconductivity, ^[13] topological states, and more.^{[ vague] [14] [15] [16] [17]} Magnetic skyrmionic bubbles have been found in Kagome metals over a wide temperature range. For example, they were observed in Fe₃Sn₂ at ~200-600 K using LTEM but with high critical field ~0.8 T. ^[18]

See also

• Herbertsmithite, a natural kagome magnet
• Magnon – Spin 1 quasiparticle; quantum of a spin wave

References