Recently, the Kagome superconductors AV3Sb5 (A = K, Rb and Cs) have attracted enormous attention due to their novel phenomena and rich physics. They exhibit unconventional charge density wave (CDW), giant anomalous Hall effect, and superconductivity. The CDW state is intimately related to the anomalous Hall effect and competes with superconductivity under pressure. Investigating the electronic structure of the CDW state is essential to understand its nature and the related physical properties.

High-resolution angle-resolved photoemission spectroscopy (ARPES) is a powerful technique to study the electronic structures of materials in the momentum space. Recently, Luo Hailan, a member of Prof. Zhou Xingjiang’s group from the Institute of Physics of the Chinese Academy of Sciences, carried out high-resolution ARPES measurements on KV3Sb5 and revealed the nature of the CDW and electron-phonon coupling in KV3Sb5.

From the ARPES measurements, the researchers observed clear evidence of the 2×2 CDW-induced electronic structure reconstruction. These include the Fermi surface reconstruction, the associated band-structure foldings between the boundary and the center of the pristine Brillouin zone, and the CDW gap openings at the boundary of the pristine and reconstructed Brillouin zones. Near the Fermi level, the Fermi surface-dependent and momentum-dependent CDW gap was measured and a strong anisotropy of the CDW gap was observed for all the V-derived Fermi surface sheets. Moreover, signatures of the electron-phonon coupling were revealed for all the V-derived bands.

These observations indicate that the electron-phonon coupling may play a dominant role in driving the CDW transition. They also provide key information in understanding the origin of the CDW and its interplay with other physical properties in AV3Sb5 Kagome superconductors.

This study was first published in Nature Communications by Andrew Shawwn.