Direct insulator to relativistic quantum Hall transition in graphene

We present evidence of the direct insulator-quantum Hall transition in monolayer epitaxial graphene, a genuine two-dimensional (2D) system. We studied the transition from an insulating state to a quantum Hall state at a high Landau level filling factor ν=6>3 and the plateau-plateau transition from ν=6 to ν=2. Using scaling theory, the critical exponent {κ} was determined to be 0.41±0.02 for the direct insulator-quantum Hall transition. This closely aligns with κ=0.42±0.02 from the ν=6 to ν=2 quantum Hall plateau-plateau transition. These findings suggest that the two transitions may belong to the same universality class. While similar transitions have been explored in conventional two-dimensional charge systems, our study provides valuable insights into a truly 2D system, deepening our understanding of these transitions.