Renormalization Group Approach to Stability of Two-dimensional Interacting Type-II Dirac Fermions

TL;DR

This paper uses renormalization group analysis to study the stability of two-dimensional type-II Dirac fermions, revealing a transition to type-I and the effects of Coulomb interactions on their stability.

Contribution

It introduces a renormalization group framework to analyze the stability and phase transition of 2D type-II Dirac fermions considering Coulomb interactions.

Findings

Tilting parameter decreases with scale, causing a transition to type-I fermions.

Photon mass is generated via chiral anomaly, leading to screening effects.

Type-II Dirac semimetals are stable against Coulomb interactions.

Abstract

The type-II Weyl/Dirac fermions are a generalization of conventional or type-I Weyl/Dirac fermions, whose conic spectrum is tilted such that the Fermi surface becomes lines in two dimensions, and surface in three dimensions rather than discrete points of the conventional Weyl/Dirac fermions. The mass-independent renormalization group calculations show that the tilting parameter decreases monotonically with respect to the length scale, which leads to a transition from two dimensional type-II Weyl/Dirac fermions to the type-I ones. Because of the non-trivial Fermi surface, a photon gains a finite mass partially via the chiral anomaly, leading to the strong screening effect of the Weyl/Dirac fermions. Consequently, anisotropic type-II Dirac semimetals become stable against the Coulomb interaction. This work provides deep insight into the interplay between the geometry of Fermi surface and the Coulomb interaction.