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

• Published in: Communications materials 2022-05, Vol.3 (1), p.1-9, Article 30
• Main Authors: Kato, Takemi, Li, Yongkai, Kawakami, Tappei, Liu, Min, Nakayama, Kosuke, Wang, Zhiwei, Moriya, Ayumi, Tanaka, Kiyohisa, Takahashi, Takashi, Yao, Yugui, Sato, Takafumi
• Format: Article
• Language: English
• Subjects: 639/301/119/2792/4128; 639/766/119/1003; 639/766/119/995; Brillouin zones; Charge density waves; Chemistry and Materials Science; Distortion; Energy gap; Fermi surfaces; First principles; Kagome lattice; Materials Science; Mathematical analysis; Photoelectric emission; Photoelectron spectroscopy; Plane waves; Quantum entanglement; Quantum phenomena; Saddle points; Spectrum analysis; Superconductivity; Topology
• ISSN: 2662-4443; 2662-4443
• DOI: 10.1038/s43246-022-00255-1

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 KV 3 Sb 5 , RbV 3 Sb 5 , and CsV 3 Sb 5 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 KV 3 Sb 5 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 KV 3 Sb 5 is investigated by angle-resolved photoemission spectroscopy and first-principles calculations, providing microscopic insight into the charge density wave and superconducting mechanisms.