Electronic Nature of Charge Density Wave and Electron-Phonon Coupling in Kagome Superconductor KV$_3$Sb$_5$

TL;DR

This study uses high-resolution ARPES to reveal the electronic structure, Fermi surface reconstruction, and electron-phonon coupling in KV3Sb5, shedding light on the charge density wave's origin and its relation to superconductivity.

Contribution

It provides detailed electronic structure measurements of KV3Sb5, demonstrating CDW-induced Fermi surface reconstruction, band folding, and anisotropic gaps, advancing understanding of CDW and superconductivity interplay.

Findings

Observation of CDW-induced Fermi surface reconstruction

Detection of band folding and gap opening at zone boundaries

Signatures of electron-phonon coupling in KV3Sb5

Abstract

The Kagome superconductors AV3Sb5 (A=K, Rb, Cs) have received enormous attention due to their nontrivial topological electronic structure, anomalous physical properties and superconductivity. Unconventional charge density wave (CDW) has been detected in AV3Sb5. High-precision electronic structure determination is essential to understand its origin. Here we unveil electronic nature of the CDW phase in our high-resolution angle-resolved photoemission measurements on KV3Sb5. We have observed CDW-induced Fermi surface reconstruction and the associated band folding. The CDW-induced band splitting and the associated gap opening have been revealed at the boundary of the pristine and reconstructed Brillouin zones. The Fermi surface- and momentum-dependent CDW gap is measured and the strongly anisotropic CDW gap is observed for all the V-derived Fermi surface. In particular, we have observed signatures of the electron-phonon coupling in KV3Sb5. These results provide key insights in understanding the nature of the CDW state and its interplay with superconductivity in AV3Sb5 superconductors.