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Edge channels of broken-symmetry quantum Hall states in graphene visualized by atomic force microscopy



Joseph A. Stroscio, Sungmin Kim, Johannes Schwenk, Daniel T. Walkup, Yihang Zeng, Fereshte Ghahari, Son T. Le, Marlou R. Slot, Julian Berwanger, Steven R. Blankenship, Kenji Watanabe, Takashi Taniguchi, Franz Giessibl, Nikolai Zhitenev, Cory Dean


The quantum Hall (QH) effect, a topologically non-trivial quantum phase, expanded and brought into focus the concept of topological order in physics. The topologically protected quantum Hall edge states are of crucial importance to the QH effect but have been measured with limited success. The QH edge states in graphene take on an even richer role as graphene is distinguished by its four-fold degenerate zero energy Landau level (zLL), where the symmetry is broken by electron interactions on top of lattice-scale potentials but has eluded spatial measurements. In this report, we map the quantum Hall broken-symmetry edge states comprising the graphene zLL at integer filling factors of ν=0,±1 across the quantum Hall edge boundary using atomic force microscopy (AFM). Measurements of the chemical potential resolve the energies of the four-fold degenerate zLL as a function of magnetic field and show the interplay of the moiré superlattice potential of the graphene/boron nitride system and spin/valley symmetry-breaking effects in large magnetic fields.
Nature Communications


graphene, atomic force microscopy, quantum hall effect


Stroscio, J. , Kim, S. , Schwenk, J. , Walkup, D. , Zeng, Y. , Ghahari, F. , Le, S. , Slot, M. , Berwanger, J. , Blankenship, S. , Watanabe, K. , Taniguchi, T. , Giessibl, F. , Zhitenev, N. and Dean, C. (2021), Edge channels of broken-symmetry quantum Hall states in graphene visualized by atomic force microscopy, Nature Communications, [online],, (Accessed April 14, 2024)
Created May 14, 2021, Updated May 21, 2021