Emergent Anti-ferromagnetism in a Y -Shaped Kekul\'e Graphene

TL;DR

This paper explores how a Y-shaped Kekulé distortion in graphene induces antiferromagnetism, revealing a tunable quantum critical point and potential for spontaneous magnetic order in graphene.

Contribution

It demonstrates that antiferromagnetic transitions in birefringent Dirac fermions can be continuously tuned and that the universality class remains consistent, providing new insights into graphene magnetism.

Findings

Quantum critical point is tunable by bond-modulation strength.

Antiferromagnetism can emerge at very small critical interactions.

Universality of quantum criticality remains in the Gross-Neveu-Heisenberg class.

Abstract

Antiferromagnetic (AF) transitions of birefringent Dirac fermions created by a Y-shaped Kekul\'e distortion in graphene are investigated by the mean-field theory and the determinant quantum Monte Carlo simulations. We show that the quantum critical point can be continuously tuned by the bond-modulation strength, and the universality of the quantum criticality remains in the Gross-Neveu-Heisenberg class. The critical interaction scales with the geometric average of the two velocities of the birefringent Dirac cones and decreases monotonically between the uniform and the completely depleted limits. Since the AF critical interaction can be tuned to very small values, antiferromagnetism may emerge automatically, realizing the long-sought magnetism in graphene. These results enrich our understanding of the semimetal-AF transitions in Dirac-fermion systems and open a new route to achieving magnetism in graphene.