Fractional Quantum Anomalous Hall Effect in Multilayer Graphene
Researchers have observed the fractional quantum anomalous Hall effect (FQAHE) in a multilayer graphene-hBN moiré superlattice. The FQAHE, which is the zero magnetic field counterpart of the fractional quantum Hall effect, has previously only been observed in twisted MoTe2. The team observed quantized Hall resistance plateaus accompanied by dips in longitudinal resistance at specific filling factors of the moiré superlattice. By tuning gate-displacement field and filling factors, the researchers also observed phase transitions between different electron states. This discovery opens up possibilities for exploring charge fractionalization and non-Abelian anyonic braiding.
Introduction to the Fractional Quantum Anomalous Hall Effect
The fractional quantum anomalous Hall effect (FQAHE) is a phenomenon that occurs in topological flat bands when there is spontaneous time-reversal-symmetry breaking. It is the zero magnetic field counterpart of the fractional quantum Hall effect. The FQAHE has potential applications in topological quantum computation due to the possibility of non-Abelian anyons.
Up until now, the FQAHE has only been observed in twisted MoTe2 at specific filling factors. However, researchers believe that graphene-based moiré superlattices could host the FQAHE with even better material quality and higher electron mobility.
Experimental Observation of FQAHE in Multilayer Graphene
In this study, researchers observed the FQAHE in a rhombohedral pentalayer graphene-hBN moiré superlattice. They observed plateaus of quantized Hall resistance at specific filling factors of the moiré superlattice, accompanied by dips in the longitudinal resistance. The Hall resistance varied linearly with the filling factor, similar to the composite Fermi liquid in the half-filled lowest Landau level at high magnetic fields.
By tuning the gate-displacement field and filling factors, the researchers were able to observe phase transitions between different electron states, including the composite Fermi liquid and FQAHE states.
Implications and Future Research
The observation of FQAHE in multilayer graphene opens up exciting possibilities for exploring charge fractionalization and non-Abelian anyonic braiding at zero magnetic field. This could have significant implications for topological quantum computation.
Additionally, the researchers highlight the potential for lateral junctions between FQAHE and superconducting regions in the same device, which could further enhance the exploration of novel quantum states and their interactions.
