Van-Hove annihilation and nematic instability on a Kagome lattice

TL;DR

This study reports the discovery of nematic order and van Hove singularities in the Kagome metal ScV6Sn6, revealing electronic symmetry breaking and potential mechanisms for correlated phases in Kagome lattice systems.

Contribution

It provides the first direct evidence of intra-unit-cell nematic order and Pomeranchuk instability in a Kagome lattice, linking electronic nematicity with Kagome physics.

Findings

Observation of stripe-like nematic order breaking lattice symmetry

Identification of van Hove singularities along specific Brillouin zone directions

Elliptical deformation of Fermi surface indicating nematic order

Abstract

Novel states of matter arise in quantum materials due to strong interactions among electrons. A nematic phase breaks the point group symmetry of the crystal lattice and is known to emerge in correlated materials. Here we report the observation of an intra-unit-cell nematic order and signatures of Pomeranchuk instability in the Kagome metal ScV6Sn6. Using scanning tunneling microscopy and spectroscopy, we reveal a stripe-like nematic order breaking the crystal rotational symmetry within the Kagome lattice itself. Moreover, we identify a set of van Hove singularities adhering to the Kagome layer electrons, which appear along one direction of the Brillouin zone while being annihilated along other high-symmetry directions, revealing a rotational symmetry breaking. Via detailed spectroscopic maps, we further observe an elliptical deformation of Fermi surface, which provides direct evidence for an electronically mediated nematic order. Our work not only bridges the gap between electronic nematicity and Kagome physics, but also sheds light on the potential mechanism for realizing symmetry-broken phases in correlated electron systems.