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Title: Precision quantization of zero-field fractional Hall states in graphene
Plain: In a true fractional quantum Hall state the sideways resistance equals an exact fraction of a natural constant and the forward resistance vanishes, and early graphene data fell short of both.
Precise: In rhombohedral multilayer graphene/hBN at $B=0$, determine whether the FQAH states at $\nu=2/3,\ 3/5$ and others reach $R_{xy}=h/(\nu e^{2})$ within 1e-3 with $R_{xx}\to0$ as $T\to0$, and extract their activation gaps. Early (2024) data had $R_{xx}$ of order kilo-ohms. An answer gives quantization accuracy and gap for each state.
Settled by: Transport at electron temperatures below 20 mK on several devices with independent contact and geometry checks.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: partially-resolved
Status note: 2025 measurements below $40\,\mathrm{mK}$ found smaller $R_{xx}$ and new FQAH states; a September 2026 preprint (arXiv:2609.09422) reports fractional quantized anomalous Hall insulators, pending independent confirmation.
Posed since: 2024