Percolation transitions in bilayer graphene encapsulated by hexagonal boron nitride

We studied the plateau-plateau transitions that characterize the electrical transport in the quantum Hall regime in a high mobility bilayer graphene flake encapsulated by hexagonal boron nitride at magnetic fields up to 9 T and temperatures above 300 mK. We measured independently the exponent κ of the temperature-induced transition broadening, the critical exponent γ of the localization length, and the exponent p ruling the temperature scaling of the coherence length, finding consistencywith the relation γ = p/2κ. The observed value of κ = 0.30(0.28,0.32) deviates from that of the quantum Hall critical point. The obtained γ = 1.25(0.96,1.54) questions the validity of a pure Anderson transition, and reveals percolation as the underlying driving mechanism.