Stability of line-node semimetals with strong Coulomb interactions and properties of the symmetry-broken state

TL;DR

This study uses diagrammatic Monte Carlo simulations to analyze the stability of line-node semimetals under Coulomb interactions, revealing a phase transition to a chiral insulator and exploring magnetic and edge state properties.

Contribution

It provides the first detailed criteria for the stability of line-node semimetals with Coulomb interactions and investigates the properties of the symmetry-broken phase.

Findings

Phase transition to a chiral insulating state at finite interaction strength

Magnetic field couples to the chiral order parameter, enabling experimental manipulation

Symmetry-broken phase hosts topological defects with metallic interface states

Abstract

We employ diagrammatic Monte Carlo simulations to establish criteria for the stability of line-node semimetals in the presence of Coulomb interactions. Our results indicate a phase transition to a chiral insulating state that occurs at a finite interaction threshold which we determine. We also compute the Landau levels for out-of-plane and in-plane magnetic fields in the symmetric and symmetry-broken phases. We find that the magnetic field couples to the chiral order parameter, implying that this degree of freedom can be manipulated in situ in experiments. Finally, we check the existence of edge states in the symmetry-broken phase. On the system's boundary, we note that the metallic "drum-head" states that exist in the symmetric phase are gapped out. However, the symmetry-broken phase permits topological defects in the macroscopic order parameter in the form of domain walls, which host metallic "interface states." These consist of line-like gap-closings that occur on the two-dimensional interfaces.