Magnetic phase transition in disordered interacting Dirac fermion systems via the Zeeman field

TL;DR

This study uses quantum Monte Carlo simulations to explore how Zeeman fields, disorder, and Coulomb interactions influence antiferromagnetic phase transitions in disordered 2D Dirac fermion systems, revealing complex interplay effects.

Contribution

It provides a detailed analysis of the combined effects of Zeeman field, disorder, and Coulomb interaction on antiferromagnetic transitions in disordered Dirac fermion systems, highlighting their interdependent roles.

Findings

Antiferromagnetic correlation increases with magnetic field at fixed U.

Disorder suppresses the magnetic field's impact on antiferromagnetic correlation.

Strong Coulomb interaction can suppress the magnetic field effect, especially beyond U_c=4.5.

Abstract

Using the determinant quantum Monte Carlo method, we investigate the antiferromagnetic phase transition that is induced by the Zeeman field in a disordered interacting two-dimensional Dirac fermion system. At a fixed interaction strength $U$, the antiferromagnetic correlation is enhanced as the magnetic filed increases, and when the magnetic field is larger than a $B_{c}(U)$, the antiferromagnetic correlation shall be suppressed by the increased magnetic field. The impact of Zeeman field $B$, Coulomb repulsion $U$ and disorder $\Delta$ is not isolated. The intensity of magnetic field effect on the antiferromagnetic correlation shall be strongly suppressed by disorder. Differently, it will be promoted by weak interaction, but when $U$ becomes larger than $U_{c}=4.5$, the increased interaction will suppress the intensity of this effect, and here $U_{c}=4.5$ coincides with the critical strength inducing the metal-Mott insulator transition in clean system. Moreover, at a fixed magnetic field $B$, strong interaction shall suppress the antiferromagnetic phase rather than promote it.