Spin Symmetry of the Bilayer Graphene Groundstate

TL;DR

This study uses nonlinear transport experiments on clean bilayer graphene to identify a spin-ordered groundstate, ruling out certain theoretical phases and narrowing down the possible gapped states.

Contribution

It provides experimental evidence for the spin-ordered phase in bilayer graphene and distinguishes it from other predicted gapped states.

Findings

Identified a spin-ordered groundstate in bilayer graphene.

Excluded the quantum anomalous Hall phase as the groundstate.

Supported the layer antiferromagnet or quantum spin Hall phase as the likely groundstates.

Abstract

We show nonlinear transport experiments on clean, suspended bilayer graphene that reveal a gap in the density of states. Looking at the evolution of the gap in magnetic fields of different orientation, we find that the groundstate is a spin-ordered phase. Of the three possible gapped groundstates that are predicted by theory for equal charge distribution between the layers, we can therefore exclude the quantum anomalous Hall phase, leaving the layer antiferromagnet and the quantum spin Hall phase as the only possible gapped groundstates for bilayer graphene.