Three-dimensional energy gap and origin of charge-density wave in kagome superconductor KV3Sb5

Kagome lattices offer a fertile ground to explore exotic quantum phenomena associated with electron correlation and band topology. The recent discovery of superconductivity coexisting with charge-density wave (CDW) in the kagome metals KV3Sb5, RbV3Sb5, and CsV3Sb5 suggests an intriguing entanglement of electronic order and superconductivity. However, the microscopic origin of CDW, a key to understanding the superconducting mechanism and its possible topological nature, remains elusive. Here, we report angle-resolved photoemission spectroscopy of KV3Sb5 and demonstrate a substantial reconstruction of Fermi surface in the CDW state that accompanies the formation of small three-dimensional pockets. The CDW gap exhibits a periodicity of undistorted Brillouin zone along the out-of-plane wave vector, signifying a dominant role of the in-plane inter-saddle-point scattering to the mechanism of CDW. The characteristics of experimental band dispersion can be captured by first-principles calculations with the inverse star-of-David structural distortion. The present result indicates a direct link between the low-energy excitations and CDW, and puts constraints on the microscopic theory of superconductivity in alkali-metal kagome lattices. Kagome metals are interesting for the coexistence of chiral charge density wave and superconductivity. Here, the structural distortion responsible for the charge density wave in KV3Sb5 is investigated by angle-resolved photoemission spectroscopy and first-principles calculations, providing microscopic insight into the charge density wave and superconducting mechanisms.

Automated summary

In this study, the structural distortion responsible for the charge density wave in KV3Sb5 is investigated using angle-resolved photoemission spectroscopy and first-principles calculations, providing microscopic insight into the charge density wave and superconducting mechanisms.