Helical edge states and fractional quantum Hall effect in a graphene electron–hole bilayer

Applying magnetic and electric fields to twisted bilayer graphene creates an electron–hole bilayer that features helical 1D edge modes and fractional quantum Hall states. Helical 1D electronic systems are a promising route towards realizing circuits of topological quantum states that exhibit non-Abelian statistics 1 , 2 , 3 , 4 . Here, we demonstrate a versatile platform to realize 1D systems made by combining quantum Hall (QH) edge states of opposite chiralities in a graphene electron–hole bilayer at moderate magnetic fields. Using this approach, we engineer helical 1D edge conductors where the counterpropagating modes are localized in separate electron and hole layers by a tunable electric field. These helical conductors exhibit strong non-local transport signals and suppressed backscattering due to the opposite spin polarizations of the counterpropagating modes. Unlike other approaches used for realizing helical states 5 , 6 , 7 , the graphene electron–hole bilayer can be used to build new 1D systems incorporating fractional edge states 8 , 9 . Indeed, we are able to tune the bilayer devices into a regime hosting fractional and integer edge states of opposite chiralities, paving the way towards 1D helical conductors with fractional quantum statistics 10 , 11 , 12 , 13 .