Electronic nature of charge density wave and electron-phonon coupling in kagome superconductor KV3Sb5

Hailin Luo ,Xiangyu Luo ,Dong Wu ,Zhirong Zhu ,Youguo Shi ,Guodong Liu ,Shaohang Wu ,Changjiang Yi ,Yuhao Gu ,Zuyan Xu ,Qiang Gao ,Xu Yu ,Junjie Jia ,Jiangping Hu ,Hongxiong Liu ,Hong Mao ,Qingyan Wang ,Kun Jiang ,Lin Zhao ,Xianju Zhou

doi:10.1038/s41467-021-27946-6

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.

Highlights

The Kagome superconductors AV3Sb5 (A = K, Rb, Cs) have received enormous attention due to their nontrivial topological electronic structure, anomalous physical properties and superconductivity
The charge density wave (CDW) state is first proposed for a one-dimensional chain of atoms with an equal spacing a which is argued to be inherently unstable against the dimerized ground state[48]
It usually involves one band with a half electron filling. This would open a CDW gap at the Fermi point kF = ±π/2a and produce a lattice reconstruction with a wavevector of π/a. Such a Fermi surface nesting picture is extended to real materials with higher dimensions where the CDW state is realized because segments of the Fermi surface are nearly parallel connected by a wavevector QCDW45

Summary

Introduction

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. The metallic Kagome lattice presents a unique electronic structure characterized by a Dirac cone at the Brillouin zone corner, von Hove singularities (VHS) at the zone boundary, and a flat band throughout the entire Brillouin zone[3,4] Such a Kagome lattice is expected to harbor topological states[3,5], fractional charges[4,6], density wave orders[3,7,8], and unconventional superconductivity[8–11]. The signature of electron–phonon coupling has been found on the V-derived bands These results provide key insight in understanding the origin of the CDW and its role on the exotic physical properties and superconductivity in Kagome superconductors

Methods

Results

Conclusion