Critical point for the CAF-F phase transition at charge neutrality in bilayer graphene

TL;DR

This study investigates the critical magnetic field at the charge neutrality point in bilayer graphene, revealing a transition from insulating to metallic states and identifying a universal scaling behavior near the phase transition.

Contribution

It experimentally identifies the critical point of the CAF-F phase transition in bilayer graphene and demonstrates its linear dependence on the perpendicular magnetic field component.

Findings

Observation of a temperature-independent crossing point in resistance.

Linear scaling of critical field with perpendicular magnetic field.

Universal resistance scaling near the transition.

Abstract

We report on magneto-transport measurements up to 30 T performed on a bilayer graphene Hall bar, enclosed by two thin hexagonal boron nitride flakes. Our high mobility sample exhibits an insulating state at neutrality point which evolves into a metallic phase when a strong in-plane field is applied, as expected for a transition from a canted antiferromagnetic to a ferromagnetic spin ordered phase. For the first time we individuate a temperature-independent crossing in the four-terminal resistance as a function of the total magnetic field, corresponding to the critical point of the transition. We show that the critical field scales linearly with the perpendicular component of the field, as expected from the underlying competition between the Zeeman energy and interaction-induced anisotropies. A clear scaling of the resistance is also found and an universal behavior is proposed in the vicinity of the transition.