Fig. 2: Ballistic transport in proximity-screened graphene.
From: Proximity screening greatly enhances electronic quality of graphene
a, Conductivity and mean free path (black and red curves, respectively). The blue dashed curve shows the n1/2 dependence expected for transport limited by edge scattering (the best fit yields ℓ ≈ 9 µm). The red line indicates the actual device width of approximately 8.5 µm. b, Ballistic transport probed by magnetic focusing. Left, map of focusing resistance R21,34(n, B) = V34/I21 (blue-to-red scale, −5 Ω to 5 Ω). The current I21 is driven between contacts 2 and 1 as shown in the inset. The voltage V34 is measured between 3 and 4. L ≈ 13.5 µm. Black dashed curves are the expected positions of the first two focusing peaks (corresponding trajectories shown in the inset). Right, vertical cuts at fixed n marked in the map by colour-coded dashed lines. c, Example of bend-resistance measurements. Insets, measurement geometry (left) and an optical micrograph of the device (right). Colour map shows R61,42 (colour scale as in b). The dashed curve is W = Dc/2, the condition where the bend resistance is expected to reverse its sign15,26. Data in a are for device S4 at 2 K. Data in b and c are for device S6 (at 20 K to suppress mesoscopics). Scale bar, 10 µm.
