The parent state in kagome metals and superconductors: Chiral-nematic Fermi liquid state

TL;DR

This paper identifies a chiral-nematic Fermi liquid as the parent state in kagome metals and superconductors, revealing its properties and transition to chiral-nematic superconductivity through spectroscopic imaging.

Contribution

It uncovers the chiral-nematic parent state in kagome materials and demonstrates its connection to exotic quantum phases and chiral superconductivity.

Findings

Multiorbital Fermi surfaces break mirror symmetries and exhibit handedness.

Direct evidence of chiral low-energy quasiparticle dispersions.

Transition from parent state to chiral-nematic superconducting state observed.

Abstract

The kagome metals and superconductors hosting rich correlated and topological electronic states have captivated quantum materials research. These states are triggered by an unconventional chiral charge density wave (CDW) wherein a chiral superconductivity emerges at low temperatures, yet the origin of this chiral CDW order, the parent state, is unresolved. Here, we report the discovery of a parent chiral-nematic Fermi liquid state in kagome metals and superconductors. We use spectroscopic-imaging scanning tunneling microscopy to study Ti-doped CsV3Sb5 where the CDW is suppressed, and find that multiorbital Fermi surfaces break all mirror reflections and exhibit handedness. We observe the chiral low-energy quasiparticle dispersions, providing direct evidence for a chiral-nematic electronic structure. We further observe the direct transition from the parent state to a chiral-nematic superconducting state. Moreover, in the samples with chiral CDW, we also observe the residual chiral-nematic QPI features, demonstrating that the CDW-triggered exotic states descend from the chiral-nematic Fermi liquid. Our findings not only provide a plausible chiral-nematic parent state, but also establish a new conceptual framework for exploring the emergence and consequences of such exotic quantum phases.