Characterizing Magnon Thermal Transport of a Quantum Hall Antiferromagnet in Bilayer Graphene

In the half-filled zero-energy Landau level of graphene, competing spin and valley orders give rise to multiple phases of quantum Hall ferromagnetism (QHFM) with spontaneously broken symmetry. Using a non-local noise thermometry technique, we measure electronic thermal conduction in bilayer graphene near charge neutrality as a function of external field strengths to explore the QHFM phase diagram. Our data show clear signatures of a phase transition between canted-antiferromagnetism (CAF) and valley-polarized states. We estimate the quantitative thermal conduction of magnons in the CAF state and study its behavior with respect to changes in different experimental parameters. Our findings constitute compelling evidence for magnon transport in quantum Hall graphene and prove that thermal transport is a powerful tool in studying strongly correlated states in mesoscale systems.