Valley Isospin Controlled Fractional Quantum Hall States in Bilayer Graphene

Ke Huang; Hailong Fu; Danielle Reifsnyder Hickey; Nasim Alem; Xi Lin; Kenji Watanabe; Takashi Taniguchi; Jun Zhu

doi:10.1103/physrevx.12.031019

Article Valley Isospin Controlled Fractional Quantum Hall States in Bilayer Graphene

Ke Huang ; Hailong Fu ; Danielle Reifsnyder Hickey ; Nasim Alem ; Xi Lin ; Kenji Watanabe (National Institute for Materials Science) ; Takashi Taniguchi (National Institute for Materials Science) ; Jun Zhu

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Ke Huang, Hailong Fu, Danielle Reifsnyder Hickey, Nasim Alem, Xi Lin, Kenji Watanabe, Takashi Taniguchi, Jun Zhu. Valley Isospin Controlled Fractional Quantum Hall States in Bilayer Graphene. Physical Review X. 2022, 12 (3), 031019. https://doi.org/10.1103/physrevx.12.031019

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Electron spin and pseudospin degrees of freedom play a critical role in many-body phenomena through exchange interactions, the understanding and control of which enable the construction of states with complex topological orders and exotic excitations. In this work, we demonstrate fine control of the valley isospin in high-quality bilayer graphene devices and its profound impact in realizing fractional quantum Hall effect with different ground state orders. We present evidence for a new even-denominator fractional quantum Hall state in bilayer graphene, its spontaneous valley polarization in the limit of zero valley Zeeman energy, and the breaking of particle-hole symmetry. These observations support the Moore-Read anti-Pfaffian order. Our experiments establish valley isospin in bilayer graphene to be a powerful experimental knob and open the door to engineering non-Abelian states and quantum information processes in a quantum Hall platform.

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