Parallel transport and layer-resolved thermodynamic measurements in twisted bilayer graphene

We employ dual-gated 30 \ifmmode^\circ\else\textdegree\fi{}-twisted bilayer graphene to demonstrate simultaneous ultrahigh mobility and conductivity (up to 40 mS at room temperature), unattainable in a single layer of graphene. We find quantitative agreement with a simple phenomenology of parallel conduction between two pristine graphene sheets, with a gate-controlled carrier distribution. Based on the parallel transport mechanism, we then introduce a method for in situ measurements of the chemical potential of the two layers. This twist-enabled approach, neither requiring a dielectric spacer, nor separate contacting, has the potential to greatly simplify the measurement of thermodynamic quantities in graphene-based systems of high current interest.