Fractional quantum anomalous Hall effect in multilayer graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Physics

Background:

• The fractional quantum anomalous Hall effect (FQAHE) is a zero-magnetic-field analogue of the fractional quantum Hall effect.
• FQAHE is predicted in topological flat bands with broken time-reversal symmetry and could enable non-Abelian anyons for topological quantum computation.
• Previous FQAHE observations were limited to twisted MoTe2 systems.

Purpose of the Study:

• To report the observation of integer and fractional quantum anomalous Hall effects in a novel graphene-based moiré superlattice.
• To investigate the potential of graphene systems for hosting FQAHE and advancing topological quantum computation.

Main Methods:

• Fabrication of a rhombohedral pentalayer graphene-hBN moiré superlattice.
• Experimental measurements of Hall resistance and longitudinal resistance at zero magnetic field.
• Tuning of gate-displacement field and moiré filling factor to observe phase transitions.

Main Results:

• Observation of quantized Hall resistance plateaus at various fractional fillings (e.g., 2/3, 3/5, 4/7) in zero magnetic field.
• Identification of a composite Fermi liquid state at half-filling (v=1/2).
• Demonstration of phase transitions between composite Fermi liquid, FQAH states, and other correlated electron states.

Conclusions:

• Rhombohedral pentalayer graphene-hBN moiré superlattices provide a promising platform for FQAHE.
• This system facilitates the exploration of charge fractionalization and non-Abelian anyonic braiding at zero magnetic field.
• The findings pave the way for developing new avenues in topological quantum computation.