Magnetic field induced semimetal-to-canted-antiferromagnet transition on the honeycomb lattice

TL;DR

This paper demonstrates that applying an in-plane magnetic field to a honeycomb lattice induces a transition from a semimetal to a canted antiferromagnetic insulator, confirmed by mean-field and quantum Monte Carlo methods.

Contribution

It reveals a magnetic-field-induced semimetal-to-antiferromagnetic insulator transition on the honeycomb lattice using combined theoretical and numerical approaches.

Findings

Magnetic field shifts spin cones, creating finite density of states.

Perfect nesting between spin Fermi sheets triggers insulating state.

Results confirmed by quantum Monte Carlo simulations.

Abstract

It is shown that the semimetallic state of the two-dimensional honeycomb lattice with a point-like Fermi surface is unstable towards a canted antiferromagnetic insulator upon application of an in-plane magnetic field. This instability is already present at the mean-field level; the magnetic field shifts the up- and the down-spin cones in opposite directions thereby generating a finite density of states at the Fermi surface and a perfect nesting between the up- and the down-spin Fermi sheets. This perfect nesting triggers a canted antiferromagnetic insulating state. Our conclusions, based on mean-field arguments, are confirmed by auxiliary field projective quantum Monte Carlo methods on lattices up to $12 \times 12$ unit cells.