Unconventional behavior of Dirac fermions in three-dimensional gauge theory

TL;DR

This paper investigates how massless Dirac fermions interact with a U(1) gauge field in two dimensions, revealing different behaviors at zero and finite chemical potential due to gauge interaction screening and velocity renormalization.

Contribution

It provides a detailed analysis of the unconventional behavior of Dirac fermions influenced by gauge fields, especially highlighting the effects of finite chemical potential on velocity renormalization.

Findings

Long-ranged gauge interactions at zero chemical potential.

Velocity renormalization due to transverse gauge interaction at finite chemical potential.

Different physical behaviors at zero and finite chemical potential.

Abstract

We study the unconventional behavior of massless Dirac fermions due to interaction with a U(1) gauge field in two spatial dimensions. At zero chemical potential, the longitudinal and transverse components of gauge interaction are both long-ranged. There is no fermion velocity renormalization since the system respects Lorentz invariance. At finite chemical potential, the Lorentz invariance is explicitly broken by the finite Fermi surface. The longitudinal gauge interaction is statically screened and becomes unimportant, whereas the transverse gauge interaction remains long-ranged and leads to singular renormalization of fermion velocity. The anomalous dimension of fermion velocity is calculated by means of the renormalization group method. We then examine the influence of singular velocity renormalization on several physical quantities, and show that they exhibit different behavior at zero and finite chemical potential.