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Topological Valley Transport at Bilayer Graphene Domain Walls

L) In bilayer graphene imaging, IR light (yellow) is focused onto the apex of a metal-coated atomic force microscope tip and the backscattered infrared radiation is collected/measured. R) At the domain wall, electrons in two valleys, K (yellow) and K’ (green), propagate in opposite directions.

Scientific Achievement
Discovered topologically protected one-dimensional channels that conduct electrons at the domain walls of bilayer graphene.

Significance and Impact
The newly-discovered conducting channels are ‘valley polarized’, which means they can serve as filters for electron valley polarization in future devices. Their existence opens possibilities for exploring unique topological phases and valley physics in graphene.

Research Details

  • Valleytronics offers an advantage in data processing speeds over the charge used in classical electronics; previous work has focused on electrons moving through 2D semiconductors
  • This study used tightly focused beams of infrared light to image in situ bilayer graphene layer-stacking domain walls on device substrates
  • Field effect devices fabricated over these domain walls revealed 1D conducting channels
  • This demonstrates that protected topological phases can be realized in bilayer graphene, a tunable semiconductor, making the 2D carbon sheets useful for valleytronics applications

L Ju, Z Shi, N Nair, Y Lv, C Jin, J Velasco, C Ojeda-Aristizabal, J Bechtel, M Martin, A Zettl, J Analytis, F Wang. Nature 520 (650-655), 2015.