Figure 1: Evolution of electron states in increasing magnetic field and design of a graphene p–n junction.

(a) A two-terminal graphene device consisting of a hole (blue) and an electron (red) cavity is sketched. By applying a weak field, the electron trajectories in the p- and n-cavities bend, leading to dispersing Fabry–Pérot resonances. (b) The field is increased until the cyclotron orbit becomes comparable to the cavity size, where resonant scar states can occur. (c) The field is further increased and transport is still described by quasiclassical cyclotron orbits. Snake states are formed along the p–n interface. (d) Finally, quantum Hall edge states propagate in opposite directions in the p- and n-region at higher fields. (e) Three-dimensional design of the measured device. The SiO₂ substrate is coloured in blue and the bottom gates in gold. The contacts, supported by the lift-off resist (green) are coloured in grey. (f) Scanning electron microscope image of a device similar to the measured sample. The graphene is coloured in blue and the bottom gates in gold. Scale bar, 1 μm.