Topological Quantum Materials with Kagome Lattice

Recently, various topological states have undergone a spurt of progress in the field of condensed matter physics. An emerging category of topological quantum materials with kagome lattice has drawn enormous attention. A two-dimensional kagome lattice composed of corner-sharing triangles is a fascinating structural system, which could not only lead to geometrically frustrated magnetism but also have a nontrivial topological electronic structure hosting Dirac points, van Hove singularities, and flat bands. Due to the existence of multiple spin, charge, and orbit degrees of freedom accompanied by the unique structure of the kagome lattice, the interplay between frustrated magnetism, nontrivial topology, and correlation effects is considered to result in abundant quantum states and provides a platform for researching the emergent electronic orders and their correlations.

In this Account, we will give an overview of our research progress on novel quantum properties in topological quantum materials with kagome lattice. Here, there are mainly two categories of kagome materials: magnetic kagome materials and nonmagnetic ones. On one hand, magnetic kagome materials mainly focus on the 3d transition-metal-based kagome systems, including Fe₃Sn₂, Co₃Sn₂S₂, YMn₆Sn₆, FeSn, and CoSn. The interplay between magnetism and topological bands manifests vital influence on the electronic response. For example, the existence of massive Dirac or Weyl fermions near the Fermi level significantly enhances the magnitude of Berry curvature in momentum space, leading to a large intrinsic anomalous Hall effect. In addition, the peculiar frustrated structure of kagome materials enables them to host a topologically protected skyrmion lattice or noncoplanar spin texture, yielding a topological Hall effect that arises from the real-space Berry phase. On the other hand, nonmagnetic kagome materials in the absence of long-range magnetic order include CsV₃Sb₅ with the coexistence of superconductivity, charge density wave state, and band topology and van der Waals semiconductor Pd₃P₂S₈. For these two kagome materials, the tunability of electric response in terms of high pressure or carrier doping helps to reveal the interplay between electronic correlation effects and band topology and discover the novel emergent quantum phenomena in kagome materials.