Charge-Density-Wave-Induced Bands Renormalization and Energy Gaps in a Kagome Superconductor RbV3Sb5

Zhonghao Liu,Yaobo Huang,Hechang Lei,Ningning Zhao,Zhengtai Liu,Kai Liu,Zhijun Tu,Wenhua Song,Qiangwei Yin,Man Li,Shancai Wang,Dawei Shen,Chunsheng Gong

doi:10.1103/physrevx.11.041010

Abstract

Recently discovered Z2 topological kagome metals AV3Sb5 (A = K, Rb, and Cs) exhibit charge density wave (CDW) phases and novel superconducting paring states, providing a versatile platform for studying the interplay between electron correlation and quantum orders. Here we directly visualize CDW-induced bands renormalization and energy gaps in RbV3Sb5 using angle-resolved photoemission spectroscopy, pointing to the key role of tuning van Hove singularities to the Fermi energy in mechanisms of ordering phases. Near the CDW transition temperature, the bands around the Brillouin zone (BZ) boundary are shifted to high-binding energy, forming an "M"-shape band with singularities near the Fermi energy. The Fermi surfaces are partially gapped and the electronic states on the residual ones should be possibly dedicated to the superconductivity. Our findings are significant in understanding CDW formation and its associated superconductivity.

Highlights

Layered kagome-lattice transition metals are emerging as an exciting platform to explore frustrated lattice geometry and quantum topology
We report on a combined angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations study of the temperature evolution of the lowenergy electronic structure in RbV3Sb5, which has a CDW transition temperature (TCDW) of about 102 K, a sign change of the Hall coefficient at about 40 K, and a superconducting transition temperature (Tc) of about 0.92 K [23]
Comparing the data taken at the two temperatures, one can see that the α band is shifted up, which is mainly attributed by surface reconstructions along with time [47]

Summary

INTRODUCTION

Layered kagome-lattice transition metals are emerging as an exciting platform to explore frustrated lattice geometry and quantum topology. The theory was put forward early that a two-dimensional (2D) energy band with saddle points in the vicinity of EF is unstable against charge-density-wave (CDW) formation [18]. X-ray diffraction and scanning tunneling microscopy (STM) reveal the formation of a three-dimensional (3D) 2 × 2 × 2 superlattice at both CDW and superconducting states [24,25,26,27,28], which energetically favors a chiral charge order and an inverse Star of David distortion in a kagome lattice with the shift of van Hove singularity to EF [34,35,40]. The CDW states and double superconducting domes are associated with multiple singularities with different energies and orbital characters near EF [27,28,29,30,31,32,33,34,35,36,37,41,42,43,44], which at

M M κ βα 0 M αβ κ

RESULTS AND DISCUSSION

CONCLUSION