Past Event

Pro QM Seminar: "Fractional Quantum Anomalous Hall Effects in Multilayer Graphene" with Zhengguang Lu

April 10, 2024
12:30 PM
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"Fractional Quantum Anomalous Hall Effects in Multilayer Graphene"

Interactions between electrons in solids often lead to exotic states of matter that are beyond single-particle pictures. One paradigmatic example is the fractional quantum Hall effect, where the Hall resistance in a two-dimensional electron gas is quantized at fractional multiples of h/e^2 in high magnetic fields. Some of these exotic fractional excitations were thought to be the key for performing topological quantum computation, in which the qubits are protected by their topological properties from the disturbance of the environment. It has been a long-standing question whether fractionally quantized Hall resistance can exist without a magnetic field until clues appeared very recently in two-dimensional materials systems. In this talk, I will present the experimental observation of the fractional quantum anomalous Hall effect, a lattice analogue of the renowned fractional quantum Hall effect at zero magnetic field, in a rhombohedral pentalayer graphene/hBN moire superlattice. Then, I will demonstrate rhombohedral pentalayer graphene/hBN as a new platform that holds significant potential for exploring fractional excitations and statistics, especially considering the uncharted big phase space spanned by the layer number, the twist angle between graphene and hBN, as well as the tuning of the gate electric field. It further paves the way to engineer the more exotic parafermions (obeying non-Abelian statistics that can be used for topological quantum computation) by combining with superconductivity.