Unconventional charge order and superconductivity in kagome metals

  • Starts: 3:30 pm on Thursday, December 2, 2021
  • Ends: 4:30 pm on Thursday, December 2, 2021
The kagome lattice — a lattice consisting of corner-sharing triangles — has been studied in the context of quantum physics for seventy years. The particular geometry of this lattice means that the electronic structure features a flat band, inflection points called ‘van Hove singularities’, and Dirac cones. Flat bands and inflection points in the band structure are natural drivers for strong interactions, while Dirac cones promote non-trivial topological effects. However, a material realizing the kagome interplay between frustrated geometry, correlations, and topology has long been in waiting. The discovery of the family of kagome metals KV3Sb5, CsV3Sb5 and RbV3Sb5 — commonly abbreviated to AV3Sb5 — recently brought this search to a successful end: Realizing the kagome band structure, these materials have been shown to exhibit superconductivity at low temperature and an unusual charge order at high temperature. I will highlight these discoveries, place them in the context of wider research efforts in topological physics and superconductivity, and add our own approaches. Specifically, I will show that the sublattice interference mechanism is central to understanding the formation of both charge order and superconductivity in these kagome metals. From there, I will outline how an unconventional charge order — exhibiting orbital currents and nematicity — can evolve, and what implications this imposes on the preferred superconducting pairing symmetry. If the hypothesis of unconventional order is substantiated, AV3Sb5 could constitute a valuable resource for building quantum matter by design and open several avenues for future research.
Claudio Chamon
Michael Denner