Strong equilibration of Landau level edge states at the physical edge of graphene

We report on the interaction of quantized Landau level (LL) edge states in graphene devices at both electrostatically defined edges of a pn junction (pnJ) and the physical edge of graphene. To determine these interactions, magnetotransport measurements were made on a graphene pnJ device with a ring shape geometry in the quantum Hall regime. Non-equilibrium conditions of the LL edge-states are established by decoupling the edge-state of the energetically lowest LL from the higher LLs at one pnJ interface. [1] Due to the chirality of these edge channels determined by the direction of the magnetic field and the charge of the carriers (n- or p-type) they then pass along the abrupt physical inner edge of the graphene ring before reaching a second pnJ which probes the level of equilibration between the lowest LL and the others. Our measurements show that, while the lowest LL edge state is decoupled from the other LL’s at the electrostatic junction [1], all of the LL edge states strongly equilibrate along the physical edge of the graphene despite the relatively short distance that they travel along this edge.
[1] N. N. Klimov, S. T. Le, J. Yan, P. Agnihotri, E. Comfort, J. U. Lee, D. B. Newell, and C. A. Richter, Phys. Rev. B 92, 241301 (2015).