Distinct band reconstructions in kagome superconductor CsV$_3$Sb$_5$

TL;DR

This study uses ARPES to reveal two distinct electronic band reconstructions in the kagome superconductor CsV$_3$Sb$_5$, highlighting the role of three-dimensional charge order and surface effects in its complex electronic structure.

Contribution

It provides the first experimental evidence of three-dimensional charge order and surface-induced orbital shifts in CsV$_3$Sb$_5$, advancing understanding of its electronic properties.

Findings

Identification of a new electron band at low temperature

Evidence for three-dimensional charge order

Surface-induced orbital-selective band shifts

Abstract

The new two-dimensional (2D) kagome superconductor CsV$_3$Sb$_5$ has attracted much recent attention due to the coexistence of superconductivity, charge order, topology and kagome physics. A key issue in this field is to unveil the unique reconstructed electronic structure, which successfully accommodates different orders and interactions to form a fertile ground for emergent phenomena. Here, we report angle-resolved photoemission spectroscopy (ARPES) evidence for two distinct band reconstructions in CsV$_3$Sb$_5$. The first one is characterized by the appearance of new electron energy band at low temperature. The new band is theoretically reproduced when the three dimensionality of the charge order is considered for a band-folding along the out-of-plane direction. The second reconstruction is identified as a surface induced orbital-selective shift of the electron energy band. Our results provide the first evidence for the three dimensionality of the charge order in single-particle spectral function, highlighting the importance of long-range out-of-plane electronic correlations in this layered kagome superconductor. They also point to the feasibility of orbital-selective control of the band structure via surface modification, which would open a new avenue for manipulating exotic phenomena in this system, including superconductivity.