Materials

1/3 Fractional and Gapless Integer Quantum Anomalous Hall States in Rhombohedral Graphene

Jackson P. Butler, Tonghang Han, Andrew DiFabbio, Zach Hadjri, Emily Aitken, Kenji Watanabe, Takashi Taniguchi, Long Ju, Raymond C. Ashoori

Featured June 7, 2026

Original Paper

AI-generated analysis — This is SciGrove's AI interpretation of the paper, not peer-reviewed content. Always refer to the original paper.

Simply

Scientists found a special "fractional" electrical state, like a tiny, perfectly organized electron dance, in a layered graphene material, which was missing before and has the biggest energy barrier to break.

In depth

The paper reports the first observation of the 1/3 fractional quantum anomalous Hall (FQAH) state in rhombohedral pentalayer graphene (R5G/hBN) at zero magnetic field, a state previously missing despite its fundamental importance in conventional FQH. The authors use quantum capacitance and transport measurements to characterize its thermodynamic gap and topological nature, revealing a surprising particle-hole symmetry in the phase diagram.

Key Takeaways

1
The 1/3 fractional quantum anomalous Hall (FQAH) state, a fundamental state in quantum Hall physics, is observed for the first time at zero magnetic field in R5G/hBN.
2
Quantum capacitance measurements provide direct thermodynamic characterization, revealing the largest gap for the 1/3 FQAH state and a topological phase transition to a trivial charge density wave.
3
The study identifies a gapless extended quantum anomalous Hall (EQAH) state, distinguishing it from the gapped integer quantum anomalous Hall (IQAH) state through compressibility measurements, despite similar transport signatures.

Conceptual Flow

HIGH LEVEL

Methodology: Probing Quantum States

The scientists used two main tools: one to measure how easily electrons can be squished (capacitance) and another to see how electricity flows (transport), to understand the material's hidden properties.

Layered Graphene Material

Measure Electron Squishiness and Flow

Material Properties Map

Results: Discovering New Quantum Phases

They discovered a new, very stable "fractional" electrical state that was previously unseen, and found that another "integer" state, while appearing stable, actually had no energy barrier.

Material Properties Map

Identify New States and Gaps

New Fractional State

Gapless Integer State

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