Topological density-wave states in a particle-hole symmetric Weyl metal

TL;DR

This paper investigates various density-wave instabilities in a particle-hole symmetric Weyl metal, revealing how different orders gap out Fermi surfaces and alter surface states, with implications for topological properties and experimental detection.

Contribution

It identifies and characterizes multiple density-wave instabilities in a Weyl metal, including their effects on Fermi surfaces and surface states, providing new insights into topological phases.

Findings

SDW_z is the leading instability for repulsive interactions.

PDW orders are the dominant instabilities for attractive interactions.

Surface states evolve into chiral Fermi lines or drumhead bands depending on the order.

Abstract

We study the instabilities of a particle-hole symmetric Weyl metal with both electron and hole Fermi surfaces (FS) around the Weyl points. For a repulsive interaction, we find that the leading instability is towards a longitudinal spin-density-wave order (SDW$_z$). Besides, there exist three degenerate subleading instabilities: a charge-density-wave (CDW) instability and two transverse spin-density-wave (SDW$_{x,y}$) instabilities. For an attractive interaction the leading instabilities are towards two pair-density-wave orders (PDW) which pair the two FS's separately. Both the PDW and SDW$_z$ order parameters fully gap out FS's, while the CDW and SDW$_{x,y}$ ones leave line nodes on both FS's. For the SDW$_z$ and the PDW states, the surface Fermi arc in the metallic state evolves to a chiral Fermi line which passes the projection of the Weyl points and traverses the full momentum space. For the CDW state, the line node projects to a "drumhead" band localized on the surface, which can lead to a topological charge polarization. We verify the surface states by numerically simulating the angular-resolved photoemission spectroscopy data.