Emergence of a new band and the Lifshitz transition in kagome metal ScV$_6$Sn$_6$ with charge density wave

TL;DR

This study uncovers a new electronic band and a Lifshitz transition in the kagome metal ScV6Sn6 associated with charge density wave formation, using ARPES, STM, and first-principles calculations, revealing complex surface and bulk electronic behaviors.

Contribution

The paper provides the first detailed analysis of temperature-dependent band changes and identifies a surface-related CDW band and a Lifshitz transition in ScV6Sn6, advancing understanding of electronic instabilities in kagome metals.

Findings

Identification of a new CDW-related surface band.

Observation of a Lifshitz transition at the CDW critical temperature.

No energy gap observed at the Fermi level, indicating a non-nesting CDW mechanism.

Abstract

Topological kagome systems have been a topic of great interest in condensed matter physics due totheir unique electronic properties. The vanadium-based kagome materials are particularly intrigu-ing since they exhibit exotic phenomena such as charge density wave (CDW) and unconventionalsuperconductivity. The origin of these electronic instabilities is not fully understood, and the re-cent discovery of a charge density wave in ScV6Sn6provides a new avenue for investigation. In thiswork, we investigate the electronic structure of the novel kagome metal ScV6Sn6using angle resolvedphotoemission spectroscopy (ARPES), scanning tunneling microscopy (STM), and first-principlesdensity functional theory calculations. Our analysis reveals for the first time the temperature-dependent band changes of ScV6Sn6and identifies a new band that exhibits a strong signatureof a structure with CDW below the critical temperature. Further analysis revealed that this newband is due to the surface kagome layer of the CDW structure. In addition, a Lifshitz transition isidentified in the ARPES spectra that is related to the saddle point moving across the Fermi levelat the critical temperature for the CDW formation. This result shows the CDW behavior may alsobe related to nesting of the saddle point, similar to related materials. However, no energy gap is observed at the Fermi level and thus the CDW is not a typical Fermi surface nesting scenario. These results provide new insights into the underlying physics of the CDW in the kagome materials and could have implications for the development of materials with new functionality.