(IMAGE)

University of Tokyo

Caption

Bilayer graphene is encapsulated on top and bottom by hexagonal boron nitride (an insulator). By applying a voltage to the top and bottom gates it is possible to control the state of the bilayer graphene. Having two gates allows for independent control of the electron density and the vertical electric field. An applied vertical electric field creates a small but significant energy difference between the top and bottom layers of graphene. This difference in energy breaks the symmetry of graphene allowing for the control of valley.

Credit

2015 Seigo Tarucha

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