Reentrant fractional quantum Hall states in bilayer graphene: Controllable, driven phase transitions

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Here we report from our theoretical studies that in biased bilayer graphene, one can induce phase transitions from an incompressible state to a compressible state by tuning the bandgap at a given electron density. Likewise, variation of the density with a fixed bandgap results in a transition from the FQHE states at lower Landau levels to compressible states at intermediate Landau levels and finally to FQHE states at higher Landau levels. This intriguing scenario of tunable phase transitions in the fractional quantum Hall states is unique to bilayer graphene and never before existed in conventional semiconductor systems.